Form N-Q

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, DC 20549

FORM N-Q


QUARTERLY SCHEDULE OF PORTFOLIO HOLDINGS OF REGISTERED MANAGEMENT INVESTMENT COMPANY

Investment Company Act file number         811-21212         

        Nuveen Insured California Tax-Free Advantage Municipal Fund         
(Exact name of registrant as specified in charter)


        333 West Wacker Drive, Chicago, Illinois 60606         
(Address of principal executive offices) (Zip code)


Jessica R. Droeger—Vice President and Secretary
        333 West Wacker Drive, Chicago, Illinois 60606         
(Name and address of agent for service)

Registrant's telephone number, including area code:         312-917-7700        

Date of fiscal year end:            8/31          

Date of reporting period:          5/31/06         

Form N-Q is to be used by management investment companies, other than small business investment companies registered on Form N-5 (§§ 239.24 and 274.5 of this chapter), to file reports with the Commission, not later than 60 days after the close of the first and third fiscal quarters, pursuant to rule 30b1-5 under the Investment Company Act of 1940 (17 CFR 270.30b1-5). The Commission may use the information provided on Form N-Q in its regulatory, disclosure review, inspection, and policymaking roles.

A registrant is required to disclose the information specified by Form N-Q, and the Commission will make this information public. A registrant is not required to respond to the collection of information contained in Form N-Q unless the Form displays a currently valid Office of Management and Budget (“OMB”) control number. Please direct comments concerning the accuracy of the information collection burden estimate and any suggestions for reducing the burden to the Secretary, Securities and Exchange Commission, 450 Fifth Street, NW, Washington, DC 20549-0609. The OMB has reviewed this collection of information under the clearance requirements of 44 U.S.C. § 3507.

Item 1. Schedule of Investments

                           Portfolio of Investments (Unaudited)             
                           Nuveen Insured California Tax-Free Advantage Municipal Fund (NKX)             
                           May 31, 2006             
        Optional         
Principal        Call         
Amount (000)    Description (1)    Provisions (2)    Ratings (3)    Value 
    Consumer Staples – 2.2% (1.5% of Total Investments)             
$          1,625    Golden State Tobacco Securitization Corporation, California, Tobacco Settlement Asset-Backed    6/13 at 100.00    BBB   $   1,944,459 
     Revenue Bonds, Series 2003A-2, 7.900%, 6/01/42             
    Health Care – 13.0% (8.6% of Total Investments)             
1,500    California Health Facilities Financing Authority, Revenue Bonds, UCSF – Stanford Healthcare,    11/08 at 101.00    AAA    1,533,375 
     Series 1998A, 5.000%, 11/15/31 – FSA Insured             
1,800    California Infrastructure Economic Development Bank, Revenue Bonds, Kaiser Hospital Assistance    8/11 at 102.00    A+    1,884,924 
     LLC, Series 2001A, 5.550%, 8/01/31             
2,000    California Statewide Community Development Authority, Hospital Revenue Bonds, Monterey    6/13 at 100.00    AAA    2,107,000 
     Peninsula Hospital, Series 2003B, 5.250%, 6/01/23 – FSA Insured             
4,060    California Statewide Community Development Authority, Revenue Bonds, Sherman Oaks Health    No Opt. Call    AAA    4,279,687 
     System, Series 1998A, 5.000%, 8/01/22 – AMBAC Insured             
1,260    Rancho Mirage Joint Powers Financing Authority, California, Revenue Bonds, Eisenhower Medical    7/14 at 100.00    A3    1,366,495 
     Center, Series 2004, 5.875%, 7/01/26             
10,620    Total Health Care            11,171,481 
    Housing/Multifamily – 1.3% (1.0% of Total Investments)             
1,165    Poway, California, Housing Revenue Bonds, Revenue Bonds, Poinsettia Mobile Home Park, Series    5/13 at 102.00    BBB+    1,170,359 
     2003, 5.000%, 5/01/23             
    Long-Term Care – 5.8% (3.8% of Total Investments)             
1,000    ABAG Finance Authority for Non-Profit Corporations, California, Insured Senior Living Revenue    11/12 at 100.00    A    1,033,330 
     Bonds, Odd Fellows Home of California, Series 2003A, 5.200%, 11/15/22             
2,000    California Health Facilities Financing Authority, Cal-Mortgage Insured Revenue Bonds, Northern    1/13 at 100.00    A    2,071,320 
     California Retired Officers Community Corporation – Paradise Valley Estates, Series 2002,             
     5.250%, 1/01/26             
1,815    California Statewide Community Development Authority, Revenue Bonds, Jewish Home for the    11/13 at 100.00    A    1,865,530 
     Aging, Series 2003, 5.000%, 11/15/18             
4,815    Total Long-Term Care            4,970,180 
    Tax Obligation/General – 48.0% (31.9% of Total Investments)             
2,000    Butte-Glenn Community College District, Butte and Glenn Counties, California, General    8/12 at 101.00    Aaa    2,066,120 
     Obligation Bonds, Series 2002A, 5.000%, 8/01/26 – MBIA Insured             
    California, General Obligation Bonds, Series 2004:             
1,000     5.125%, 2/01/27    2/14 at 100.00    A    1,034,510 
500     5.250%, 4/01/34    4/14 at 100.00    A    521,240 
    California, General Obligation Refunding Bonds, Series 2002:             
1,500     5.000%, 2/01/12    No Opt. Call    A    1,585,425 
3,750     5.000%, 4/01/27 – AMBAC Insured    4/12 at 100.00    AAA    3,846,788 
3,000     5.250%, 4/01/30 – XLCA Insured    4/12 at 100.00    AAA    3,158,280 
450    Fremont Unified School District, Alameda County, California, General Obligation Bonds, Series    8/12 at 101.00    AAA    466,304 
     2002A, 5.000%, 8/01/25 – FGIC Insured             
    Hacienda La Puente Unified School District, Los Angeles County, California, General Obligation             
    Bonds, Series 2003B:             
4,500     5.000%, 8/01/26 – FSA Insured    8/13 at 100.00    AAA    4,648,770 
2,030     5.000%, 8/01/27 – FSA Insured    8/13 at 100.00    AAA    2,093,356 
10,500    Los Angeles Unified School District, California, General Obligation Bonds, Series 2003A,    7/13 at 100.00    AAA    10,925,457 
     5.000%, 7/01/22 – FSA Insured             
2,000    Los Angeles, California, General Obligation Bonds, Series 2002A, 5.000%, 9/01/22 – MBIA Insured    9/12 at 100.00    AAA    2,081,340 
1,000    Murrieta Valley Unified School District, Riverside County, California, General Obligation    9/13 at 100.00    AAA    1,033,380 
     Bonds, Series 2003A, 5.000%, 9/01/26 – FGIC Insured             
    Oakland Unified School District, Alameda County, California, General Obligation Bonds,             
    Series 2005:             
190     5.000%, 8/01/25 – MBIA Insured    8/15 at 100.00    AAA    197,566 
200     5.000%, 8/01/26 – MBIA Insured    8/15 at 100.00    AAA    207,508 
3,000    San Diego Unified School District, California, General Obligation Bonds, Election of 1998,    7/10 at 100.00    AAA    3,151,830 
     Series 2000B, 5.125%, 7/01/22 – MBIA Insured             
    San Jose-Evergreen Community College District, Santa Clara County, California, General             
    Obligation Bonds, Series 2005A:             
145     5.000%, 9/01/25 – MBIA Insured    9/15 at 100.00    AAA    151,263 
215     5.000%, 9/01/27 – MBIA Insured    9/15 at 100.00    AAA    223,293 
3,855    San Rafael City High School District, Marin County, California, General Obligation Bonds,    8/12 at 100.00    AAA    3,956,502 
     Series 2003A, 5.000%, 8/01/28 – FSA Insured             
39,835    Total Tax Obligation/General            41,348,932 
    Tax Obligation/Limited – 43.2% (28.7% of Total Investments)             
550    Baldwin Park Public Financing Authority, California, Sales Tax and Tax Allocation Bonds,    8/13 at 102.00    BBB    570,922 
     Puente Merced Redevelopment Project, Series 2003, 5.250%, 8/01/21             
2,025    Burbank Public Financing Authority, California, Revenue Refunding Bonds, Golden State    12/13 at 100.00    AAA    2,147,877 
     Redevelopment Project, Series 2003A, 5.250%, 12/01/22 – AMBAC Insured             
2,000    California State Public Works Board, Lease Revenue Bonds, Department of Corrections, Series    12/13 at 100.00    A–    2,162,720 
     2003C, 5.500%, 6/01/16             
4,000    California State Public Works Board, Lease Revenue Bonds, Department of General Services,    12/12 at 100.00    AAA    4,105,960 
     Capital East End Project, Series 2002A, 5.000%, 12/01/27 – AMBAC Insured             
1,610    Folsom Public Financing Authority, California, Special Tax Revenue Bonds, Series 2004A,    9/12 at 102.00    AAA    1,673,289 
     5.000%, 9/01/21 – AMBAC Insured             
130    Hesperia Community Redevelopment Agency, California, Tax Allocation Bonds, Series 2005A,    9/15 at 100.00    AAA    135,916 
     5.000%, 9/01/20 – XLCA Insured             
5,540    Irvine Public Facilities and Infrastructure Authority, California, Assessment Revenue Bonds,    9/06 at 103.00    AAA    5,713,291 
     Series 2003C, 5.000%, 9/02/21 – AMBAC Insured             
1,770    Los Angeles Unified School District, California, Certificates of Participation, Administration    10/12 at 100.00    AAA    1,813,790 
     Building Project II, Series 2002C, 5.000%, 10/01/27 – AMBAC Insured             
2,000    Los Angeles, California, Certificates of Participation, Municipal Improvement Corporation,    6/13 at 100.00    AAA    2,044,420 
     Series 2003AW, 5.000%, 6/01/33 – AMBAC Insured             
1,500    Los Osos, California, Improvement Bonds, Community Services Wastewater Assessment District 1,    9/10 at 103.00    AAA    1,535,700 
     Series 2002, 5.000%, 9/02/33 – MBIA Insured             
500    Paramount Redevelopment Agency, California, Tax Allocation Bonds, Redevelopment Project    8/13 at 100.00    AAA    520,890 
     Area 1, Series 2003, 5.000%, 8/01/19 – MBIA Insured             
150    Rialto Redevelopment Agency, California, Tax Allocation Bonds, Merged Project Area, Series    9/15 at 100.00    AAA    153,390 
     2005A, 5.000%, 9/01/35 – XLCA Insured             
315    Riverside County Public Financing Authority, California, Tax Allocation Bonds, Multiple    10/15 at 100.00    AAA    322,173 
     Projects, Series 2005A, 5.000%, 10/01/35 – XLCA Insured             
    San Buenaventura, California, Certificates of Participation, Golf Course Financing Project,             
    Series 2002D:             
3,000     5.000%, 2/01/27 – AMBAC Insured    2/12 at 100.00    AAA    3,067,320 
3,300     5.000%, 2/01/32 – AMBAC Insured    2/12 at 100.00    AAA    3,363,822 
1,200    San Diego Redevelopment Agency, California, Subordinate Lien Tax Increment and Parking Revenue    9/09 at 101.00    Baa2    1,232,760 
     Bonds, Centre City Project, Series 2003B, 5.250%, 9/01/26             
2,770    San Jose Financing Authority, California, Lease Revenue Refunding Bonds, Civic Center Project,    6/12 at 100.00    AAA    2,831,466 
     Series 2002B, 5.000%, 6/01/32 – AMBAC Insured             
1,220    San Jose Redevelopment Agency, California, Tax Allocation Bonds, Merged Area Redevelopment    8/10 at 101.00    AAA    1,245,120 
     Project, Series 2002, 5.000%, 8/01/32 – MBIA Insured             
2,390    Solano County, California, Certificates of Participation, Series 2002, 5.250%, 11/01/24 –    11/12 at 100.00    AAA    2,533,926 
     MBIA Insured             
35,970    Total Tax Obligation/Limited            37,174,752 
    Transportation – 14.1% (9.4% of Total Investments)             
5,480    Bay Area Governments Association, California, BART SFO Extension, Airport Premium Fare Revenue    8/12 at 100.00    AAA    5,627,248 
     Bonds, Series 2002A, 5.000%, 8/01/26 – AMBAC Insured             
2,000    Foothill/Eastern Transportation Corridor Agency, California, Toll Road Revenue Bonds, Series    1/10 at 100.00    BBB–    1,956,740 
     1995A, 5.000%, 1/01/35             
1,300    San Francisco Airports Commission, California, Revenue Bonds, San Francisco International    5/10 at 101.00    AAA    1,346,098 
     Airport, Second Series 2000, Issue 26B, 5.000%, 5/01/25 – FGIC Insured             
3,135    San Francisco Airports Commission, California, Revenue Bonds, San Francisco International    5/08 at 101.00    AAA    3,224,755 
     Airport, Second Series Issue 16B, 5.000%, 5/01/24 – FSA Insured             
11,915    Total Transportation            12,154,841 
    U.S. Guaranteed – 4.9% (3.2% of Total Investments) (4)             
1,000    Berryessa Union School District, Santa Clara County, California, General Obligation Bonds,    8/12 at 100.00    AAA    1,068,880 
     Series 2003C, 5.000%, 8/01/21 (Pre-refunded 8/01/12) – FSA Insured             
1,000    California Health Facilities Financing Authority, Revenue Bonds, Cedars-Sinai Medical Center,    12/09 at 101.00    A3 (4)    1,092,310 
     Series 1999A, 6.250%, 12/01/34 (Pre-refunded 12/01/09)             
1,940    California Statewide Community Development Authority, Revenue Bonds, Sherman Oaks Health    8/08 at 102.00    AAA    2,032,150 
     System, Series 1998A, 5.000%, 8/01/22 (Pre-refunded 8/01/08) – AMBAC Insured             
3,940    Total U.S. Guaranteed            4,193,340 
    Utilities – 5.7% (3.8% of Total Investments)             
1,000    Anaheim Public Finance Authority, California, Second Lien Electric Distribution Revenue Bonds,    10/14 at 100.00    AAA    1,066,250 
     Series 2004, 5.250%, 10/01/21 – MBIA Insured             
3,055    Los Angeles Department of Water and Power, California, Power System Revenue Bonds, Series    7/11 at 100.00    AAA    3,217,495 
     2001A-1, 5.250%, 7/01/22 – FSA Insured             
275    Los Angeles Department of Water and Power, California, Power System Revenue Bonds, Series    7/13 at 100.00    AAA    285,684 
     2003A-2, 5.000%, 7/01/21 – MBIA Insured             
310    Merced Irrigation District, California, Electric System Revenue Bonds, Series 2005, 5.125%,    9/15 at 100.00    AAA    321,535 
     9/01/31 – XLCA Insured             
4,640    Total Utilities            4,890,964 
    Water and Sewer – 12.1% (8.1% of Total Investments)             
215    Healdsburg Public Financing Authority, California, Wastewater Revenue Bonds, Series 2006,    4/16 at 100.00    AAA    221,641 
     5.000%, 4/01/36 (WI/DD, Settling 6/06/06) – MBIA Insured             
490    Los Angeles Department of Water and Power, California, Waterworks Revenue Bonds, Series    7/16 at 100.00    AAA    510,271 
     2006A-2, 5.000%, 7/01/27 – AMBAC Insured             
1,125    Manteca Financing Authority, California, Sewerage Revenue Bonds, Series 2003B, 5.000%,    12/13 at 100.00    Aaa    1,128,488 
     12/01/33 – MBIA Insured             
    San Diego Public Facilities Financing Authority, California, Subordinate Lien Water Revenue             
    Bonds, Series 2002:             
3,000     5.000%, 8/01/22 – MBIA Insured    8/12 at 100.00    AAA    3,121,590 
2,500     5.000%, 8/01/23 – MBIA Insured    8/12 at 100.00    AAA    2,596,225 
1,180    South Feather Water and Power Agency, California, Water Revenue Certificates of Participation,    4/13 at 100.00    BBB    1,208,344 
     Solar Photovoltaic Project, Series 2003, 5.375%, 4/01/24             
1,600    Sunnyvale Financing Authority, California, Water and Wastewater Revenue Bonds, Series 2001,    10/11 at 100.00    AAA    1,637,840 
     5.000%, 10/01/26 – AMBAC Insured             
10,110    Total Water and Sewer            10,424,399 
$      124,635    Total Investments (cost $125,369,246) – 150.3%            129,443,707 
    Other Assets Less Liabilities – 1.9%            1,683,216 
    Preferred Shares, at Liquidation Value – (52.2)%            (45,000,000) 
    Net Assets Applicable to Common Shares – 100%           $   86,126,923 

    At least 80% of the Fund’s net assets (including net assets attributable to Preferred shares) are invested 
    in municipal securities that are either covered by Original Issue Insurance, Secondary Market Insurance or 
    Portfolio Insurance which ensures the timely payment of principal and interest. Up to 20% of the Fund’s 
    net assets (including net assets attributable to Preferred shares) may be invested in municipal securities 
    that are (i) either backed by an escrow or trust containing sufficient U.S. Government or U.S. Government 
    agency securities (also ensuring the timely payment of principal and interest), or (ii) rated, at the time 
    of investment, within the four highest grades (Baa or BBB or better by Moody’s, S&P or Fitch) or unrated 
    but judged to be of comparable quality by the Adviser. 
(1)    All percentages shown in the Portfolio of Investments are based on net assets applicable to Common 
    shares unless otherwise noted. 
(2)    Optional Call Provisions: Dates (month and year) and prices of the earliest optional call or redemption. 
    There may be other call provisions at varying prices at later dates. Certain mortgage-backed securities 
    may be subject to periodic principal paydowns. 
(3)    Ratings: Using the higher of Standard & Poor’s or Moody’s rating. Ratings below BBB by Standard & Poor’s 
    Group or Baa by Moody’s Investor Service, Inc. are considered to be below investment grade. 
(4)    Backed by an escrow or trust containing sufficient U.S. Government or U.S. Government agency securities 
    which ensure the timely payment of principal and interest. Such investments are normally considered to 
    be equivalent to AAA rated securities. 
WI/DD    Purchased on a when-issued or delayed delivery basis. 

Income Tax Information

The following information is presented on an income tax basis. Differences between amounts for financial statement and federal income tax purposes are primarily due to the treatment of paydown gains and losses, timing differences in recognizing taxable market discount and timing differences in recognizing certain gains and losses on investment transactions.

At May 31, 2006, the cost of investments was $126,332,412.

Gross unrealized appreciation and gross unrealized depreciation of investments at May 31, 2006, were as follows:

Gross unrealized:     
  Appreciation    $4,130,520 
  Depreciation    (1,019,225) 
Net unrealized appreciation (depreciation) of investments    $3,111,295 

Item 2. Controls and Procedures.

  1. The registrant's principal executive and principal financial officers, or persons performing similar functions, have concluded that the registrant's disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940, as amended (the "1940 Act") (17 CFR 270.30a-3(c))) are effective, as of a date within 90 days of the filing date of this report that includes the disclosure required by this paragraph, based on their evaluation of the controls and procedures required by Rule 30a-3(b) under the 1940 Act (17 CFR 270.30a-3(b)) and Rule 13a-15(b) or 15d-15(b) under the Securities Exchange Act of 1934 (17 CFR 240.13a-15(b) or 240.15d-15(b)).
  2. There were no changes in the registrant's internal control over financial reporting (as defined in Rule 30a-3(d) under the 1940 Act (17 CFR 270.30a-3(d)) that occurred during the registrant's last fiscal quarter that have materially affected, or are reasonably likely to materially affect, the registrant's internal control over financial reporting.

Item 3. Exhibits.

File as exhibits as part of this Form a separate certification for each principal executive officer and principal financial officer of the registrant as required by Rule 30a-2(a) under the 1940 Act (17 CFR 270.30a-2(a)), exactly as set forth below: EX-99 CERT Attached hereto.


SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

(Registrant)         Nuveen Insured California Tax-Free Advantage Municipal Fund        

By (Signature and Title)*          /s/ Jessica R. Droeger                     
                                                    Jessica R. Droeger
                                                    Vice President and Secretary

Date         July 28, 2006        

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

By (Signature and Title)*         /s/ Gifford R. Zimmerman                    
                                                   Gifford R. Zimmerman
                                                   Chief Administrative Officer (principal executive officer) 

Date         July 28, 2006        

By (Signature and Title)*         /s/ Stephen D. Foy                              
                                                   Stephen D. Foy
                                                   Vice President and Controller (principal financial officer) 

Date        July 28, 2006        

* Print the name and title of each signing officer under his or her signature.