UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13G

                    Under the Securities Exchange Act of 1934

                         (Amendment No. ______________)*

                                  Watsco, Inc.
--------------------------------------------------------------------------------
                                (Name of Issuer)

                                  Common Stock
--------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                    942622200
                  ---------------------------------------------
                                 (CUSIP Number)

                                December 31, 2003
         --------------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)

     Check the appropriate box to designate the rule pursuant to which this
Schedule is filed:

                                [x] Rule 13d-1(b)
                                [_] Rule 13d-1(c)
                                [_] Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).

                               Page 1 of 10 pages



----------------------------                         ---------------------------
CUSIP No.  942622200                 13G             Page 2 of 10 Pages
          ------------------
----------------------------                         ---------------------------

--------------------------------------------------------------------------------
  1    NAME OF REPORTING PERSON
       S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

         Columbia Wanger Asset Management, L.P. 36-3820584
--------------------------------------------------------------------------------
  2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

         Not Applicable                                                  (a) [_]

                                                                         (b) [_]
--------------------------------------------------------------------------------
  3    SEC USE ONLY

--------------------------------------------------------------------------------
  4    CITIZENSHIP OR PLACE OF ORGANIZATION

         Delaware
--------------------------------------------------------------------------------
                     5     SOLE VOTING POWER
   NUMBER OF
                             None
    SHARES         -------------------------------------------------------------
  BENEFICIALLY       6     SHARED VOTING POWER

    OWNED BY                 1,625,000
      EACH         -------------------------------------------------------------
   REPORTING         7     SOLE DISPOSITIVE POWER

    PERSON                   None
     WITH          -------------------------------------------------------------
                     8     SHARED DISPOSITIVE POWER

                             1,625,000
--------------------------------------------------------------------------------
  9    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

         1,625,000
--------------------------------------------------------------------------------
  10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*

         Not Applicable                                                      [_]
--------------------------------------------------------------------------------
  11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

         7.2 %
--------------------------------------------------------------------------------
  12   TYPE OF REPORTING PERSON*

         IA
--------------------------------------------------------------------------------



----------------------------                         ---------------------------
CUSIP No.  942622200                 13G             Page 3 of 10 Pages
          ------------------
----------------------------                         ---------------------------

--------------------------------------------------------------------------------
  1    NAME OF REPORTING PERSON
       S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

         WAM Acquisition GP, Inc.
--------------------------------------------------------------------------------
  2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

         Not Applicable                                                  (a) [_]

                                                                         (b) [_]
--------------------------------------------------------------------------------
  3    SEC USE ONLY

--------------------------------------------------------------------------------
  4    CITIZENSHIP OR PLACE OF ORGANIZATION

         Delaware
--------------------------------------------------------------------------------
                     5     SOLE VOTING POWER
   NUMBER OF
                             None
    SHARES         -------------------------------------------------------------
  BENEFICIALLY       6     SHARED VOTING POWER

    OWNED BY                 1,625,000
      EACH         -------------------------------------------------------------
   REPORTING         7     SOLE DISPOSITIVE POWER

    PERSON                   None
     WITH
                   -------------------------------------------------------------
                     8     SHARED DISPOSITIVE POWER

                             1,625,000
--------------------------------------------------------------------------------
  9    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

         1,625,000
--------------------------------------------------------------------------------
  10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*

         Not Applicable                                                      [_]
--------------------------------------------------------------------------------
  11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

         7.2 %
--------------------------------------------------------------------------------
  12   TYPE OF REPORTING PERSON*

         CO
--------------------------------------------------------------------------------



----------------------------                         ---------------------------
CUSIP No.  942622200                 13G             Page 3 of 10 Pages
          ------------------
----------------------------                         ---------------------------

--------------------------------------------------------------------------------
  1    NAME OF REPORTING PERSON
       S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

         Columbia Acorn Trust
--------------------------------------------------------------------------------
  2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

         Not Applicable                                                  (a) [_]

                                                                         (b) [_]
--------------------------------------------------------------------------------
  3    SEC USE ONLY

--------------------------------------------------------------------------------
  4    CITIZENSHIP OR PLACE OF ORGANIZATION

         Massachusetts
--------------------------------------------------------------------------------
                     5     SOLE VOTING POWER
   NUMBER OF
                             None
    SHARES         -------------------------------------------------------------
  BENEFICIALLY       6     SHARED VOTING POWER

    OWNED BY                 1,525,000
      EACH         -------------------------------------------------------------
   REPORTING         7     SOLE DISPOSITIVE POWER

    PERSON                   None
     WITH
                   -------------------------------------------------------------
                     8     SHARED DISPOSITIVE POWER

                             1,525,000
--------------------------------------------------------------------------------
  9    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

         1,525,000
--------------------------------------------------------------------------------
  10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*

         Not Applicable                                                      [_]
--------------------------------------------------------------------------------
  11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

         6.8 %
--------------------------------------------------------------------------------
  12   TYPE OF REPORTING PERSON*

         IV
--------------------------------------------------------------------------------



Item 1(a)      Name of Issuer:

                        Watsco, Inc.

Item 1(b)      Address of Issuer's Principal Executive Offices:

                        2665 South Bayshore Drive
                        Suite 901
                        Coconut Grove, FL  33133

Item 2(a)      Name of Person Filing:

                        Columbia Wanger Asset Management, L.P. ("WAM")
                        WAM Acquisition GP, Inc., the general partner of WAM
                         ("WAM GP")
                        Columbia Acorn Trust ("Acorn")


Item 2(b)      Address of Principal Business Office:

                        WAM, WAM GP, and Acorn are located at:

                        227 West Monroe Street, Suite 3000
                        Chicago, Illinois  60606

Item 2(c)      Citizenship:

                        WAM is a Delaware limited partnership; WAM GP is a
                        Delaware corporation; Acorn is a Massachusetts business
                        trust.

Item 2(d)      Title of Class of Securities:

                        Common Stock

Item 2(e)      CUSIP Number:

                        942622200

Item 3         Type of Person:

                        (d)    Acorn is an Investment Company under section 8
                               of the Investment Company Act.

                        (e)    WAM is an Investment Adviser registered under
                               section 203 of the Investment Advisers Act of
                               1940; WAM GP is the General Partner of the
                               Investment Adviser.

                               Page 5 of 10 pages



Item 4   Ownership (at December 31, 2003):

               (a)   Amount owned "beneficially" within the meaning of rule
                     13d-3:

                     1,625,000

               (b)   Percent of class:

                     7.2 % (based on 22,541,871 shares outstanding as of
                     November 3, 2003)

               (c)   Number of shares as to which such person has:

                        (i)     sole power to vote or to direct the vote: none

                        (ii)    shared power to vote or to direct the vote:
                                1,625,000

                        (iii)   sole power to dispose or to direct the
                                disposition of: none

                        (iv)    shared power to dispose or to direct disposition
                                of: 1,625,000

Item 5   Ownership of Five Percent or Less of a Class:

               Not Applicable

Item 6   Ownership of More than Five Percent on Behalf of Another Person:

               The shares reported herein have been acquired on behalf of
               discretionary clients of WAM, including Acorn. Persons other
               than WAM and WAM GP are entitled to receive all dividends from,
               and proceeds from the sale of, those shares. Acorn is the only
               such person known to be entitled to all dividends from, and all
               proceeds from the sale of, shares reported herein to the extent
               of more than 5% of the class.

Item 7   Identification and Classification of the Subsidiary Which Acquired the
         Security Being Reported on by the Parent Holding Company:

               Not Applicable

Item 8   Identification and Classification of Members of the Group:

               Not Applicable

Item 9   Notice of Dissolution of Group:

               Not Applicable

                               Page 6 of 10 pages



Item 10        Certification:

                        By signing below I certify that, to the best of my
               knowledge and belief, the securities referred to above were
               acquired and are held in the ordinary course of business and
               were not acquired and are not held for the purpose of or with
               the effect of changing or influencing the control of the issuer
               of the securities and were not acquired and are not held in
               connection with or as a participant in any transaction having
               that purpose or effect.

                               Page 7 of 10 Pages



                                    Signature

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

Date:  February 13, 2004

                     The undersigned corporation, on the date above written,
                     agrees and consents to the joint filing on its behalf of
                     this Schedule 13G in connection with its beneficial
                     ownership of the security reported herein.

                              WAM Acquisition GP, Inc.
                               for itself and as general partner of
                               COLUMBIA WANGER ASSET
                               MANAGEMENT, L.P.

                              By:  /s/ Bruce H. Lauer
                                   ---------------------------------------
                                       Bruce H. Lauer
                                       Senior Vice President and Secretary

                     The undersigned corporation, on the date above written,
                     agrees and consents to the joint filing on its behalf of
                     this Schedule 13G in connection with its beneficial
                     ownership of the security reported herein.

                              COLUMBIA ACORN TRUST


                              By:  /s/ Bruce H. Lauer
                                   ---------------------------------------
                                       Bruce H. Lauer
                                       Vice President, Treasurer and
                                       Secretary

                               Page 8 of 10 Pages



                                  Exhibit Index

Exhibit 1   Joint Filing Agreement dated as of February 13, 2004 by and among
            Columbia Wanger Asset Management, L.P., WAM Acquisition GP, Inc. and
            Columbia Acorn Trust.

                               Page 9 of 10 Pages



                                                                       EXHIBIT 1

                             JOINT FILING AGREEMENT

     The undersigned hereby agree to the joint filing of the Schedule 13G to
which this Agreement is attached.

                 Dated:  February 13, 2004

                                          WAM Acquisition GP, Inc.
                                            for itself and as general partner of
                                            COLUMBIA WANGER ASSET
                                            MANAGEMENT, L.P.

                                          By: /s/ Bruce H. Lauer
                                              ----------------------------------
                                                  Bruce H. Lauer
                                                  Senior Vice President and
                                                  Secretary

                                          COLUMBIA ACORN TRUST

                                          By: /s/ Bruce H. Lauer
                                              ----------------------------------
                                                  Bruce H. Lauer
                                                  Vice President, Treasurer and
                                                  Secretary

                               Page 10 of 10 pages