<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 30,1999.
                  -----------------



                  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") a September 30, 1999 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, 1999 and the results of its operations and cash flows for the
three months ended September 30, 1999.

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's revenues for the third quarter of 1999 consisted of
partnership transfer fees of $50. Expenses for the third quarter of 1999
consisted of general and administrative costs of $1,907, management fees of
$500, insurance of $36 and real estate taxes of $2,297.

         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
$2,080, 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.


                                        2
<PAGE>   3

         The Partnership had no revenues for the second quarter of 1999.
Expenses for the second quarter of 1999 consisted of general and administrative
costs of $3,125, management fees of $3,750, insurance of $37 and real estate
taxes of $2,359.

         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 first quarter of 1999 consisted of
partnership transfer fees in the amount of $50. Expenses for the first quarter
of 1999 consisted of general and administrative costs of $1,444, management fees
of $3,750, insurance of $37 and real estate taxes of $2,358.

         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 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 $15,000 to $30,000 per developed acre and undeveloped raw
land (little of which is being sold) is selling for less than $5,000 an acre.
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 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.


                                        3
<PAGE>   4

         Liquidity and Capital Resources
         -------------------------------

         The Partnership has no cash reserve remaining at September 30, 1999. 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 $373,100 at
September 30, 1999. 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.

         During 1998, a potential purchaser made an offer for approximately
$4,750 an acre but subsequently withdrew it upon further investigation.


         Impact of Year 2000
         -------------------

         The Partnership has assessed and is continuing to assess its operating
systems, computer software applications, computer equipment and other equipment
with embedded electronic circuits ("Programs") that it currently uses to
identify whether they are Year 2000 compliant and, if not, what steps are needed
to bring them into compliance. The Partnership expects all Programs to be
compliant by December 31, 1999. However, the Partnership is reviewing the
potential impact on the Partnership and the alternatives that are available to
it if the Programs cannot be brought into compliance by December 31, 1999. The
Partnership believes that the required changes to its Programs will be made on a
timely basis without causing material operational issues or having a material
impact on its results of operations on its financial position.

         The Partnership believes that its core business of owning improved land
is not heavily dependent on the Year 2000 compliance of its Programs and that,
should a reasonably likely worst case Year 2000 situation occur, the
Partnership, because of the basic nature of its systems, many of which can be
executed manually, would not likely suffer material loss or disruption in
remedying the situation.

         The costs incurred and expected to be incurred in the future regarding
Year 2000 compliance have been and are expected to be immaterial to the results
of operations and financial position of the Partnership. Costs related to Year
2000 compliance are expensed as incurred.

         The Partnership has been reviewing whether its significant third party
service providers including financial institutions ("Providers") are Year 2000
compliant. The Company is not aware


                                        4
<PAGE>   5

of any Providers that do not expect to be compliant; however, the Company has no
means of ensuring that its Providers will be Year 2000 ready. The inability of
Providers to be Year 2000 ready in a timely fashion could have an adverse impact
on the Company. The Company plans to respond to any such contingency involving
any of its Providers by seeking to utilize alternative sources for such goods
and services, where practicable. In addition, widespread disruptions in the
national or international economy, including, for example, disruptions affecting
financial markets, and commercial and investment banks, could also have an
adverse impact on the Company. The likelihood and effects of such disruptions
are not determinable at this time.

         Quantitative and Qualitative Disclosures About Market Risk
         ----------------------------------------------------------

         The Partnership's primary market risk exposure relates to general
economic trends effecting the overall real estate market as it relates to the
holding of land for investment purposes.

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. ss.221.1 et
seq. The Partnership is not a direct party to the order, but ownership of the
stock of the General 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 1999.


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.


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<PAGE>   6

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 1999. However, see Item 5 below.

Item 5 - Other Information

         The Partnership entered into an Agreement of Sale ("Agreement") with
Diamond Ventures, Inc. ("Diamond") on August 10, 1999, which has been
subsequently amended on September 3, 1999; October 4, 1999; and October 12,
1999. Under the Agreement, as amended, the Partnership will sell all 118 acres
of the Partnership's land to Diamond for $450,000. Diamond has completed its due
diligence and placed $150,000 into escrow. The sale is conditioned upon approval
by the holders of a majority of the Limited Partnership Units. Equity Products
Corporation, an affiliate of the General Partner, currently owns 75% of the
Limited Partnership Units and has agreed to vote in favor of the sale after it
receives the approval of the Court handling the rehabilitation proceedings in
which its ultimate parent, Fidelity Mutual Life Insurance Company (In
Rehabilitation), is currently engaged.

         Upon consummation of the sale to Diamond, the Partnership will be
dissolved and liquidated. Any liquidation proceeds remaining after payment of
the Partnership's obligations and the expenses of liquidation will be
distributed to the Partners in accordance with the provisions of the Partnership
Agreement.


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)
-----------------------------------------------------------------

Exhibit Numbers         Description                                 Page Number
---------------         -----------                                 -----------

3.1(a)                  Certificate of Limited                      *
                        Partnership

3.1(b) & (4)            Restated Limited Partnership                **
                        Agreement

9                       not applicable

11                      not applicable


                                        6
<PAGE>   7

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
--------------------------------------------------------------------------------

*    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.


                                       7
<PAGE>   8






                                    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,                     11/09/1999
-------------------------            Treasurer,                     ----------
    Arthur W. Mullin                 Director of
                                     FMG Western
                                     Region
                                     Acquisitions, Inc.







/s/ Margaret M. Tamasitis             Assistant Secretary           11/09/1999
-------------------------             of FMG Western                ----------
    Margaret M. Tamasitis             Region
                                      Acquisitions, Inc.



                                        8
<PAGE>   9


EXHIBIT A

                       FMG RITA RANCH LIMITED PARTNERSHIP

                                 BALANCE SHEETS

                                     ASSETS
                                     ------
<TABLE>
<CAPTION>


                                September 30,      December 31,
                                    1999              1998
                                 (Unaudited)
                                -------------      ------------

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

Cash and cash equivalents               644               544
                                   --------          --------
                                   $350,644          $350,544
                                   ========          ========


                        LIABILITIES AND PARTNERS' EQUITY
                        --------------------------------

LIABILITIES:

Accrued expenses                   $ 11,789          $ 20,002

Due to affiliates                        --             3,750

Partners' Equity                    338,855           326,792
                                   --------          --------
                                   $350,644          $350,544
                                   ========          ========

</TABLE>



                                        1
<PAGE>   10


                      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,
                                            1999                1998                1999                 1998
                                        -------------       -------------       -------------       -------------
<S>                                    <C>                 <C>                 <C>                 <C>
REVENUES:
  Interest income                           $      0            $      0            $      0            $      0
  Other income                                    50                   0                 100                   0
                                        -------------       -------------       -------------       -------------
                                                  50                   0                 100                   0
                                        -------------       -------------       -------------       -------------


EXPENSES:
  Real estate taxes                            2,297               2,598               7,014               7,075
  Management fees                                500               3,750               8,000              11,250
  General and administrative                   1,907               2,089               6,476               7,523
  Insurance                                       36                  30                 110                  89
                                        -------------       -------------       -------------       -------------
                                               4,740               8,467              21,600              25,937


          NET LOSS                          $ (4,690)           $ (8,467)           $(21,500)           $(25,937)

Partners' equity,
   Beginning of period                       339,314             339,697             326,792             336,863
Captial Contributions                          4,231               4,527              33,563              24,831
                                        -------------       -------------       -------------       -------------

Partners' equity,
   End of period                            $338,855            $335,757            $338,855            $335,757
                                        =============       =============       =============       =============

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

Loss from Operations per
   Limited Partnership
   Interest                                 $   (.69)           $  (1.24)           $  (3.17)           $  (3.82)
                                        =============       =============       =============       =============

</TABLE>


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<PAGE>   11

                      F M G RITA RANCH LIMITED PARTNERSHIP

                  STATEMENTS OF OPERATIONS AND PARTNERS' EQUITY

                                   (Unaudited)



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

<S>                                   <C>                <C>                <C>
                                          1999             1998             1997
                                     --------------   --------------   --------------
REVENUES:
  Interest income                         $      0         $      0         $      3
  Other income                                 100                0              300
                                     --------------   --------------   --------------
                                               100                0              303
                                     --------------   --------------   --------------

EXPENSES:
  Real estate taxes                          7,014            7,075            6,716
  Management fees                            8,000           11,250           11,250
  General and administrative                 6,476            7,523            4,172
  Insurance                                    110               89               81
                                     --------------   --------------   --------------
                                            21,600           25,937           22,219
                                     --------------   --------------   --------------
          NET LOSS                        $(21,500)        $(25,937)        $(21,916)
                                     ==============   ==============   ==============

</TABLE>

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<PAGE>   12


                      F M G RITA RANCH LIMITED PARTNERSHIP

                            STATEMENTS OF CASH FLOWS

                                   (Unaudited)
<TABLE>
<CAPTION>
                                                          FOR THE NINE MONTHS
                                                          ENDED SEPTEMBER 30
                                            ----------------------------------------------
                                                1999             1998             1997
                                            ------------     ------------     ------------

<S>                                         <C>              <C>              <C>

CASH FLOWS FROM OPERATING ACTIVITIES:
     Net income (loss)                         $(21,500)        $(25,937)        $(21,916)
     Adjustments to reconcile net
       income (loss) to net cash
       used in operating activities:

     Increase in General Partner's
       capital                                   33,563           24,831           21,438
     Increase (decrease) in
       accrued expenses                          (8,213)           4,856            4,480
     Increase (decrease) in
       due to affiliate                          (3,750)          (3,750           (3,750)
                                            ------------     ------------     ------------
     Net cash provided by (used in)
       operating activities                    $    100         $      0         $    252
                                            ------------     ------------     ------------


     Cash, Beginning of period                      544         $    519         $    267


     Cash, End of period                       $    644         $    519         $    519
                                            ============     ============     ============

</TABLE>

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