<PAGE>   1
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, DC  20549
                                   Form 10-Q



  X             
------          QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15 (D) OF THE 
                SECURITIES EXCHANGE ACT OF 1934 FOR THE QUARTERLY PERIOD
                ENDED SEPTEMBER  30, 1998.
                      --------------------
                
                
                
------          TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (D) OF THE
                SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD
                FROM                        TO                           .
                     ----------------------    -------------------------- 



Commission File number:  0-16601 (formerly 33-16164-LA)
                         ------------------------------


                       FMG RITA RANCH LIMITED PARTNERSHIP
                       ----------------------------------
                           (Exact name of registrant)

Delaware                                                    23-2466343
--------                                                    ----------

(State or other jurisdiction of                    (I.R.S. Employer
incorporation or organization)                     Identification No.)

250 King of Prussia Road, Radnor, PA  19087
-------------------------------------------
(Address of Principal Executive Offices)

Issuer's Telephone Number:  (610 964-7234)
                            --------------

Indicate by check mark whether the registrant (a) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports) and (2) has been subject to such
filing requirements for the past 90 days.  Yes   x     No 
                                                ---       ---
<PAGE>   2
PART I - FINANCIAL INFORMATION

Item 1 - Financial Statements

     The unaudited financial statements of FMG Rita Ranch Limited partnership
(the "Partnership") at September 30, 1998 are attached hereto as Exhibit A.

     In the opinion of management, the accompanying unaudited condensed
financial statements include all adjustments, which are of a normal recurring
nature, necessary to present fairly the Partnership's financial position as of
September 30, 1998, and the results of its operations and cash flows for the
three months ended September 30, 1998.

Item 2 - Management's Discussion and Analysis of Financial Condition and
Results of Operations.

     Background

     The Partnership is a Delaware limited partnership.  The Partnership was
formed on January 30, 1987 by FMG Western Region Acquisitions, Inc. (the
"General Partner") and the initial limited partner, FM Initial, Inc., with an
initial contribution of $25,000 by the General Partner.  The General Partner is
an indirect wholly-owned subsidiary of The Fidelity Mutual Life Insurance
Company (in Rehabilitation) ("Fidelity Mutual").  In accordance with the
Amended and Restated Limited partnership Agreement dated December 17, 1987 (the
"Partnership Agreement"), FM Initial, Inc. withdrew from the partnership upon
admittance of new limited partners.  The Partnership was formed to acquire and
realize appreciation in a certain 118 acre parcel of undeveloped land near
Tucson, Arizona (the "Property") by holding it for investment and eventual
sale, although there is no assurance that this will be attained.

     Results of Operations

     The Partnership had no revenues for the third quarter of 1998. Expenses
for the third quarter of 1998 consisted of general and administrative costs of
$2,089, management fees of $3,750, insurance of $30 and real estate taxes of
$2,598.

     The Partnership's revenues for the third quarter of 1997 consisted of
partnership transfer fees in the amount of $225. Expenses for the third quarter
of 1997 consisted of general and administrative costs of $1,262, management
fees of $3,750, insurance of $27 and real estate taxes of $1,983.

     The Partnership's revenues for the third quarter of 1996 consisted of
interest income of $1 and partnership transfer fees of $25. Expenses for the
third quarter of 1996 consisted of general



                                       2
<PAGE>   3
and administrative costs of $1,179, management fees of $3,750, insurance of $35
and real estate taxes of $1,892.

     The Partnership had no revenues for the second quarter of 1998. Expenses
for the second quarter of 1998 consisted of general and administrative costs of
$2,067, management fees of $3,750, insurance of $29 and real estate taxes of
$2,238.

     The Partnership's revenues for the second quarter of 1997 consisted of
interest income of $1 and partnership transfer fees of $75. Expenses for the
second quarter of 1997 consisted of general and administrative costs of $1,655,
management fees of $3,750, insurance of $27 and real estate taxes of $2,366.

     The Partnership's revenues for the second quarter of 1996 consisted of
interest income of $2 and partnership transfer fees of $25. Expenses for the
second quarter of 1996 consisted of  general and administrative costs of
$1,875, management fees of $3,750, insurance of $34 and real estate taxes of
$2,604.

     The Partnership had no revenues for the first quarter of 1998. Expenses
for the first quarter of 1998 consisted of general and administrative costs of
$3,367, management fees of $3,750, insurance of $30 and real estate taxes of
$2,239.

     The Partnership's revenues for the first quarter of 1997 consisted of
interest income of $2. Expenses for the first quarter of 1997 consisted of
general and administrative costs of $1,255, management fees of $3,750,
insurance of $27 and real estate taxes of $2,367.

     The Partnership's revenues for the first quarter of 1996 consisted of
interest income of $2 and partnership transfer fees of $75. Expenses for the
first quarter of 1996 consisted of general and administrative costs of $1,430,
management fees of $3,750, insurance of $35 and real estate taxes of $2,604.

     The General Partner has no plans to develop the Property, except for
activities including land planning, market surveys and other activities
necessary to prepare the Property for sale. There can be no assurance that
necessary funds would be available should it be desirable for the Partnership
to improve the Property to facilitate its sale.

     Because of the lack of demand for industrial and commercial land in the
Tucson area and the resulting decline in the Property's value, the Partnership
was required to reduce its carrying value on the Property in 1990 and again in
1992. Class "A" Business Park lots dominate the industrial land sales market.
Sale prices range from $1.00 to $2.15 per square foot for 5 to 20 acre parcels.
There have not been any bulk sale transactions since the RTC was disposing of
it's properties. The General Partner believes that it would be necessary for
the Partnership to hold the property for several years, possibly decades,
before the Partnership may be able to sell the



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<PAGE>   4
Property at a price which approximates the price paid by the Partnership for
the Property. Thus, it is unlikely that the Property will be sold for a price
which approximates the original price paid by the Partnership for the Property.
The Partnership anticipates a sale price of $4,000 to $5,000 per acre.

     During 1990 and 1992, the Partnership recorded writedowns of $6,261,041
and $830,000 respectively.

     Liquidity and Capital Resources

     The Partnership has no cash reserve remaining at September 30, 1998.  As
shown in the accompanying financial statements, the Partnership has incurred
substantial operating losses in each of the past three years.  Such losses will
continue until the Partnership begins to sell land parcels.  In the partnership
agreement, the General Partner has committed to contribute up to $600,000 to
the capital of the Partnership as the need for additional working capital
arises.  Cumulative amounts funded by the General Partner amounted to $319,450
at September 30, 1998.  Realization of the partnership's assets is dependent
upon the continued funding of operating deficits by the General Partner and its
affiliate.  There can be no assurance, however, that the General Partner or its
affiliate will continue to fund operating deficits.

     The property is listed for sale with Grubb & Ellis of Tucson, Arizona. The
listing is from March 1, 1998 to November 30, 1998.  A sale price of $4,000 to
$5,000 an acre is anticipated.

     Impact of Year 2000

     The Partnership's management has assessed the Year 2000 technology issue,
and has developed an action plan to address the issue. Management believes that
its action plan will be implemented and completed in a timely fashion, and that
it will not materially affect the Partnership's future operating results or
future financial condition.

PART II - OTHER INFORMATION

Item 1 - Legal Proceedings

     The Partnership is not a direct party to, nor is the Partnership's
property directly the subject of, any material legal proceedings.  However, on
November 6, 1992, the Commonwealth Court of Pennsylvania issued an order
placing The Fidelity Mutual Life Insurance Company ("Fidelity Mutual"), the
indirect parent of the General Partner of the Partnership, into rehabilitation
under the control and authority of the Pennsylvania Insurance Commissioner
pursuant to the provisions of the Pennsylvania Insurance Department Act, 40
P.S. Section 221.1 et seq.  The Partnership is not a direct party to the order,
but ownership of the stock of the General




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<PAGE>   5
Partner and the stock of the majority Limited Partner is vested in the
Insurance Commissioner pursuant to the Order.

Item 2 - Changes in Securities

     There was no change in the partnership's securities during the third
quarter of 1998.


Item 3 - Defaults Upon Senior Securities

     There was no default in the payment of principal, interest, a sinking or
purchase fund installment or any other default with respect to any indebtedness
of the Partnership.  The Partnership has issued no preferred stock;
accordingly, there has been no arrearages or delinquencies with respect to any
such preferred stock.


Item 4 - Submission of Matters to a Vote of Security Holders

     No matters were submitted to the Partners for a vote during the third
quarter of 1998.


Item 5 - Other Information

     None


Item 6 - Exhibits and Reports on Form 8-K

Reports on Form 8-K

     None

Exhibits (numbered in accordance with Item 601 of Regulation S-K)

<TABLE>
<CAPTION>
Exhibit Numbers           Description                               Page Number
---------------           -----------                               -----------
<S>                       <C>                                       <C>
3.1(a)                    Certificate of Limited                    *
                          Partnership

3.1(b) & (4)              Restated Limited Partnership              **
                          Agreement
</TABLE>



                                       5
<PAGE>   6
<TABLE>
<S>                       <C>
9                         not applicable

11                        not applicable

12                        not applicable

13                        not applicable

16                        not applicable

18                        not applicable

19                        not applicable

22                        not applicable

23                        not applicable

24                        not applicable

25                        not applicable

28                        not applicable

29                        not applicable
</TABLE>

--------------------------------------------------------------------------------
*Incorporated by reference to Exhibit 3.1 filed as part of the Exhibits to the
Partnership's Registration Statement on Form S-18, Registration No.
33-16164-LA.

**   Incorporated by reference to Exhibit 3.2 filed as part of the partnership's
Registration Statement on Form S-18, Registration No. 33-16164-LA.



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<PAGE>   7
                                   SIGNATURE


     Pursuant to the requirements of the Securities Exchange Act of 1934, this
Report has been signed below by the following persons on behalf of the
Registrant and in the capacities and on the date indicated.


Signature                                Title                   Date    
---------                                -----                   ----    


/s/ ARTHUR W. MULLIN                     President,             11/6       1998
----------------------------------       Treasurer,         --------------     
Arthur W. Mullin                         Director of                     
                                         FMG Western                     
                                         Region                          
                                         Acquisitions,                   
                                         Inc.                            
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
/s/ JAMES W. KELICAN, JR.                Vice President,        11/6       1998
----------------------------------       Director of        --------------     
James W. Kelican, Jr.                    FMG Western                    
                                         Region                         
                                         Acquisitions,      
                                         Inc.               
                                                                





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<PAGE>   8
EXHIBIT A

                       FMG RITA RANCH LIMITED PARTNERSHIP

                                 BALANCE SHEETS

                                     ASSETS


<TABLE>
<CAPTION>
                                                           September 30,          December 31
                                                               1998                  1997
                                                            (Unaudited)
                                                           --------------         -----------

<S>                                                       <C>                    <C>
Land held for sale, net                                   $      350,000         $   350,000

Cash and cash equivalents                                            519                 519
                                                           --------------         -----------

                                                          $      350,519         $   350,519
                                                           ==============         ===========


                         LIABILITIES AND PARTNERS' EQUITY

LIABILITIES:

   Accrued expenses                                       $       14,762         $     9,906

   Due to affiliates                                                    -              3,750

   Partners' Equity                                              335,757             336,863
                                                           --------------         -----------

                                                          $      350,519         $   350,519
                                                           ==============         ===========
</TABLE>


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<PAGE>   9
                      F M G RITA RANCH LIMITED PARTNERSHIP

                 STATEMENTS OF OPERATIONS AND PARTNERS' EQUITY

                                  (Unaudited)

<TABLE>
<CAPTION>
                                          Three months           Three months           Nine months         Nine months
                                              ended                  ended                 ended               ended
                                          September 30,          September 30,         September 30,       September 30,
                                              1998                   1997                   1998                1997
                                        ------------------    --------------------    -----------------    -------------
<S>                                   <C>                   <C>                     <C>                  <C>
REVENUES:
  Interest income                     $                 0   $                   0   $                0   $            3
  Other income                                          0                     225                    0              300
                                        ------------------    --------------------    -----------------    -------------

                                                        0                     225                    0              303
                                        ------------------    --------------------    -----------------    -------------


EXPENSES:
  Real estate taxes                                 2,598                   1,983                7,075            6,716
  Management fees                                   3,750                   3,750               11,250           11,250
  General and administrative                        2,089                   1,262                7,523            4,172
  Insurance                                            30                      27                   89               81
                                        ------------------    --------------------    -----------------    -------------

                                                    8,467                   7,022               25,937           22,219
                                        ------------------    --------------------    -----------------    -------------


          NET LOSS                    $            (8,467)  $              (6,797)  $          (25,937)  $      (21,916)

Partners' equity,
   Beginning of period                            339,697                 339,388              336,863          336,856

Captial Contributions                               4,527                   3,787               24,831           21,438
                                        ------------------    --------------------    -----------------    -------------

Partners' equity,
   End of period                      $           335,757   $             336,378   $          335,757   $      336,378
                                        ==================    ====================    =================    =============

Weighted Average Number of
   Limited Partnership Units
   Outstanding                                      6,707                   6,707                6,707            6,707
                                        ==================    ====================    =================    =============


Loss from Operations per
   Limited Partnership
   Interest                                        $(1.24)                 $(1.00)              $(3.82)          $(3.23)
                                        ==================    ====================    =================    =============
</TABLE>

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<PAGE>   10

                      F M G RITA RANCH LIMITED PARTNERSHIP

                      STATEMENTS OF OPERATIONS AND PARTNER

                                  (Unaudited)




<TABLE>
<CAPTION>
                                                       NINE MONTHS
                                                    ENDED SEPTEMBER 30
                                    --------------------------------------------------

                                       1998                1997               1996
                                    ------------    -------------------   ------------
<S>                               <C>             <C>                    <C>
REVENUES:
  Interest income                 $           0   $                  3   $          5
  Other income                                0                    300            125
                                    ------------    -------------------    -----------

                                              0                    303            130
                                    ------------    -------------------    -----------

EXPENSES:
  Real estate taxes                       7,075                  6,716          7,100
  Management fees                        11,250                 11,250         11,250
  General and administrative              7,523                  4,172          4,484
  Insurance                                  89                     81            104
                                    ------------    -------------------    -----------

                                         25,937                 22,219         22,938
                                    ------------    -------------------    -----------

          NET LOSS                $     (25,937)  $            (21,916)  $    (22,808)
                                    ============    ===================    ===========
</TABLE>

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<PAGE>   11
                      F M G RITA RANCH LIMITED PARTNERSHIP

                            STATEMENTS OF CASH FLOWS

                                  (Unaudited)


<TABLE>
<CAPTION>
                                                      FOR THE NINE MONTHS
                                                      ENDED SEPTEMBER 30
                                            ---------------------------------------

                                                1998          1997         1996
                                            -------------  -----------  -----------
<S>                                        <C>            <C>          <C>
CASH FLOWS FROM OPERATING ACTIVITIES:

Net income (loss)                          $    (25,937)  $  (21,916)  $  (22,808)
Adjustments to reconcile net
  income (loss) to net cash
  used in operating activities:

  Increase in General Partner's
    capital                                      24,831       21,438       22,140
  Increase (decrease) in
    accrued expenses                              4,856        4,480        4,458
  Increase (decrease) in
    due to affiliate                             (3,750)      (3,750)      (3,750)
                                            -------------  -----------  -----------
  Net cash provided by (used in)
    operating activities                   $          0   $      252   $       40
                                            -------------  -----------  -----------


   Cash, Beginning of period                        519          267          205


   Cash, End of period                     $        519   $      519   $      245
                                            =============  ===========  ===========
</TABLE>


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