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


                                  SCHEDULE 13G


                   Under the Securities Exchange Act of 1934

                              (Amendment No. 9 )*
                                            ---

                         Monarch Casino & Resort, Inc.
--------------------------------------------------------------------------------
                                (Name of Issuer)

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

                                   609027107
                 ---------------------------------------------
                                 (CUSIP Number)

                               December 31, 2002
            -------------------------------------------------------
            (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
SEC 1745 (2/92)

CUSIP No. 609027107                    13G                    Page 2 of 10 Pages

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

           Liberty 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
--------------------------------------------------------------------------------
     NUMBER OF         5    SOLE VOTING POWER

       SHARES                   None
                       ---------------------------------------------------------
    BENEFICIALLY       6    SHARED VOTING POWER

      OWNED BY                  852,700
                       ---------------------------------------------------------
        EACH           7    SOLE DISPOSITIVE POWER

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

                                852,700
--------------------------------------------------------------------------------
  9    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           852,700
--------------------------------------------------------------------------------
  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

           9.0 %
--------------------------------------------------------------------------------
  12   TYPE OF REPORTING PERSON*

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

CUSIP No. 609027107                    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
--------------------------------------------------------------------------------
     NUMBER OF         5    SOLE VOTING POWER

       SHARES                   None
                       ---------------------------------------------------------
    BENEFICIALLY       6    SHARED VOTING POWER

      OWNED BY                  852,700
                       ---------------------------------------------------------
        EACH           7    SOLE DISPOSITIVE POWER

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

                                852,700
--------------------------------------------------------------------------------
  9    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           852,700
--------------------------------------------------------------------------------
  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

           9.0 %
--------------------------------------------------------------------------------
  12   TYPE OF REPORTING PERSON*

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

CUSIP No. 609027107                    13G                    Page 4 of 10 Pages

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

           Liberty 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
--------------------------------------------------------------------------------
     NUMBER OF         5    SOLE VOTING POWER

       SHARES                   None
                       ---------------------------------------------------------
    BENEFICIALLY       6    SHARED VOTING POWER

      OWNED BY                  635,000
                       ---------------------------------------------------------
        EACH           7    SOLE DISPOSITIVE POWER

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

                                635,000
--------------------------------------------------------------------------------
  9    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           635,000
--------------------------------------------------------------------------------
  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

           6.7 %
--------------------------------------------------------------------------------
  12   TYPE OF REPORTING PERSON*

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

Item 1(a)               Name of Issuer:

                            Monarch Casino & Resort, Inc.

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

                            1175 W. Moana Lane
                            Suite 200
                            Reno, NV 89509

Item 2(a)               Name of Person Filing:

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


Item 2(b)               Address of Principal Business Office:

                            WAM, WAM GP and Acorn are all 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; and Acorn is a Massachusetts
                            business trust.

Item 2(d)               Title of Class of Securities:

                            Common Stock

Item 2(e)               CUSIP Number:

                            609027107

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, 2002):

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

                                  852,700

                            (b)   Percent of class:

                                  9.0 % (based on 9,474,830 shares outstanding
                                  as of November 12, 2002).

                            (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:  852,700
                                  (iii)   sole power to dispose or to direct the
                                          disposition of:  none
                                   (iv)   shared power to dispose or to direct
                                          disposition of:  852,700

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 4, 2003


                        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
                                          LIBERTY 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.


                                        LIBERTY 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 4, 2003 by
                        and among Liberty Wanger Asset Management, L.P., WAM
                        Acquisition GP, Inc. and Liberty Acorn Trust


                               Page 9 of 10 Pages