<PAGE>   1


                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549



                                    Form 10-Q



                Quarterly Report Pursuant to Section 13 or 15(d)
                     of the Securities Exchange Act of 1934



                For the Quarterly Period Ended September 30, 1999


                           Commission File No. 1-8032



                          SAN JUAN BASIN ROYALTY TRUST


            Texas                                      I.R.S. No. 75-6279898


                     Bank One, Texas, N.A., Trust Department
                                 P. O. Box 2604
                             Fort Worth, Texas 76113

                          Telephone Number 817/884-4630


Indicate by check mark whether the registrant (1) 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 and (2) has been subject to such filing requirements for
the past 90 days. Yes  X   No
                      ---     ---

Number of units of beneficial interest outstanding at November 12, 1999:
46,608,796



<PAGE>   2



                          SAN JUAN BASIN ROYALTY TRUST

                         PART I - FINANCIAL INFORMATION


Item 1.  Financial Statements.

The condensed financial statements included herein have been prepared by Bank
One, Texas, N.A. as Trustee for the San Juan Basin Royalty Trust (the "Trust"),
without audit, pursuant to the rules and regulations of the Securities and
Exchange Commission. Certain information and footnote disclosures normally
included in annual financial statements have been condensed or omitted pursuant
to Rule 10-01 of Regulation S-X promulgated under the Securities and Exchange
Act of 1934, although the Trustee believes that the disclosures are adequate to
make the information presented not misleading. These condensed financial
statements should be read in conjunction with the financial statements and the
notes thereto included in the Trust's annual report on Form 10-K for the year
ended December 31, 1998. In the opinion of the Trustee, all adjustments,
consisting only of normal recurring adjustments, necessary to present fairly the
assets, liabilities and trust corpus of the San Juan Basin Royalty Trust at
September 30, 1999, and the distributable income and changes in trust corpus for
the three-month and nine-month periods ended September 30, 1999 and 1998 have
been included. The distributable income for such interim periods is not
necessarily indicative of the distributable income for the full year.

Deloitte & Touche LLP, independent certified public accountants, has conducted a
limited review of the condensed financial statements as of September 30, 1999
and for the three-month and nine-month periods ended September 30, 1999 and 1998
included herein.


                                      -2-

<PAGE>   3


INDEPENDENT ACCOUNTANTS' REPORT


Bank One, Texas, N.A. as Trustee
   for the San Juan Basin Royalty Trust:

We have reviewed the accompanying condensed statement of assets, liabilities and
trust corpus of the San Juan Basin Royalty Trust as of September 30, 1999 and
the related condensed statements of distributable income and changes in trust
corpus for the three-month and nine-month periods ended September 30, 1999 and
1998. These financial statements are the responsibility of the Trustee.

We conducted our reviews in accordance with standards established by the
American Institute of Certified Public Accountants. A review of interim
financial information consists principally of applying analytical procedures to
financial data and making inquiries of persons responsible for financial and
accounting matters. It is substantially less in scope than an audit conducted in
accordance with generally accepted auditing standards, the objective of which is
the expression of an opinion regarding the financial statements taken as a
whole. Accordingly, we do not express such an opinion.

The accompanying condensed financial statements are prepared on a modified cash
basis as described in Note 1, which is a comprehensive basis of accounting other
than generally accepted accounting principles.

Based on our reviews, we are not aware of any material modifications that should
be made to such condensed financial statements for them to be in conformity with
the basis of accounting described in Note 1.

We have previously audited, in accordance with generally accepted auditing
standards, the statement of assets, liabilities and trust corpus of the San Juan
Basin Royalty Trust as of December 31, 1998, and the related statements of
distributable income and changes in trust corpus for the year then ended (not
presented herein); and in our report dated March 22, 1999, we expressed an
unqualified opinion on those financial statements. In our opinion, the
information set forth in the accompanying condensed statement of assets,
liabilities and trust corpus as of December 31, 1998 is fairly stated, in all
material respects, in relation to the statement of assets, liabilities and trust
corpus from which it has been derived.




DELOITTE & TOUCHE LLP

November 11, 1999

                                      -3-

<PAGE>   4
SAN JUAN BASIN ROYALTY TRUST

CONDENSED STATEMENTS OF ASSETS, LIABILITIES AND TRUST CORPUS
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
                                                                           SEPTEMBER 30,    DECEMBER 31,
                                                                              1999             1998
                                                                           (UNAUDITED)

<S>                                                                      <C>              <C>
ASSETS

Cash and short-term investments                                          $    2,622,256   $    2,665,562
Net overriding royalty interest in producing
   oil and gas properties (net of accumulated
   amortization of $86,409,491 and $82,187,508
   at September 30, 1999 and December 31, 1998, respectively)                46,866,037       51,088,020
                                                                         --------------   --------------

                                                                         $   49,488,293   $   53,753,582
                                                                         ==============   ==============

LIABILITIES AND TRUST CORPUS

Distribution payable to Unit holders                                     $    2,622,256   $    2,665,562
Commitments and contingencies
Trust corpus - 46,608,796 Units of beneficial
   interest authorized and outstanding                                       46,866,037       51,088,020
                                                                         --------------   --------------

                                                                         $   49,488,293   $   53,753,582
                                                                         ==============   ==============
</TABLE>

CONDENSED STATEMENTS OF DISTRIBUTABLE INCOME (UNAUDITED)
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
                                      THREE MONTHS ENDED              NINE MONTHS ENDED
                                         SEPTEMBER 30,                   SEPTEMBER 30,
                                -----------------------------   -----------------------------
                                     1999            1998            1999            1998
<S>                             <C>             <C>             <C>             <C>
Royalty income                  $   7,908,631   $   6,276,679   $  20,313,662   $  24,618,472
Interest income                        13,147          12,749          42,876          57,951
Other                                    --              --           892,496            --
                                -------------   -------------   -------------   -------------
                                    7,921,778       6,289,428      21,249,034      24,676,423

General and administrative
   expenditures                       156,248         125,509         747,712         663,603
                                -------------   -------------   -------------   -------------

Distributable income            $   7,765,530   $   6,163,919   $  20,501,322   $  24,012,820
                                =============   =============   =============   =============

Distributable income per Unit
   (46,608,796 Units)           $     .166611   $     .132248   $     .439860   $     .515199
                                =============   =============   =============   =============
</TABLE>


The accompanying notes to condensed financial statements are an integral part of
these statements.


                                      -4-

<PAGE>   5




SAN JUAN BASIN ROYALTY TRUST

CONDENSED STATEMENTS OF CHANGES IN TRUST CORPUS  (UNAUDITED)
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
                                                   THREE MONTHS ENDED                  NINE MONTHS ENDED
                                                     SEPTEMBER 30,                        SEPTEMBER 30,
                                           --------------------------------    --------------------------------
                                                 1999              1998              1999              1998

<S>                                        <C>               <C>               <C>               <C>
Trust corpus, beginning of period          $   48,340,628    $   53,419,624    $   51,088,020    $   56,119,448
Amortization of net overriding
   royalty interest                            (1,474,591)       (1,177,023)       (4,221,983)       (3,876,847)
Distributable income                            7,765,530         9,604,967        20,501,322        24,012,820
Distributions declared                         (7,765,530)       (9,604,967)      (20,501,322)      (24,012,820)
                                           --------------    --------------    --------------    --------------

Trust corpus, end of period                $   46,866,037    $   52,242,601    $   46,866,037    $   52,242,601
                                           ==============    ==============    ==============    ==============
</TABLE>


The accompanying notes to condensed financial statements are an integral part of
these statements.


                                      -5-




<PAGE>   6


SAN JUAN BASIN ROYALTY TRUST

NOTES TO CONDENSED FINANCIAL STATEMENTS (UNAUDITED)
--------------------------------------------------------------------------------

1.    BASIS OF ACCOUNTING

      The San Juan Basin Royalty Trust was established as of November 1, 1980.
      The financial statements of the Trust are prepared on the following basis:

      o   Royalty income recorded for a month is the amount computed and paid by
          the working interest owner, Burlington Resources Oil & Gas Company
          ("BROG"), to the Trustee for the Trust. Royalty income consists of the
          amounts received by the owner of the interest burdened by the net
          overriding royalty interest ("Royalty") from the sale of production
          less accrued production costs, development and drilling costs,
          applicable taxes, operating charges, and other costs and deductions,
          multiplied by 75%. The Royalty income amount of $20,313,662 for the
          nine months ended September 30, 1999, does not include the $892,496
          paid to the Trust for a one-time business interruption insurance
          claim.

      o   Trust expenses recorded are based on liabilities paid and cash
          reserves established from Royalty income for liabilities and
          contingencies.

      o   Distributions to Unit holders are recorded when declared by the
          Trustee.

      o   The conveyance which transferred the overriding royalty interest to
          the Trust provides that any excess of production costs over gross
          proceeds must be recovered from future net profits.

      The financial statements of the Trust differ from financial statements
      prepared in accordance with generally accepted accounting principles
      ("GAAP") because revenues are not accrued in the month of production;
      certain cash reserves may be established for contingencies which would not
      be accrued in financial statements prepared in accordance with GAAP; and
      amortization of the Royalty calculated on a unit-of-production basis is
      charged directly to trust corpus.

2.    FEDERAL INCOME TAXES

      For federal income tax purposes, the Trust constitutes a fixed investment
      trust which is taxed as a grantor trust. A grantor trust is not subject to
      tax at the trust level. The Unit holders are considered to own the Trust's
      income and principal as though no trust were in existence. The income of
      the Trust is deemed to have been received or accrued by each Unit holder
      at the time such income is received or accrued by the Trust rather than
      when distributed by the Trust.

      The Royalty constitutes an "economic interest" in oil and gas properties
      for federal income tax purposes. Unit holders must report their share of
      the revenues of the Trust as ordinary income from oil and gas royalties
      and are entitled to claim depletion with respect to such income. The
      Royalty is treated as a single property for depletion purposes.

      The Trust has on file technical advice memoranda confirming the tax
      treatment described above.

      The Trust began receiving royalty income from coal seam gas wells
      beginning in 1989. Under Section 29 of the Internal Revenue Code, coal
      seam gas production from wells drilled prior to January 1, 1993 (including
      certain wells recompleted in coal seams formations thereafter), generally
      qualifies for the federal income tax credit for producing non-conventional
      fuels if such production and the sale thereof occurs before January 1,
      2003. For 1998, this tax credit was $1.06 per MMBtu. For qualifying
      production of the Trust, each Unit holder must determine his pro rata
      share of such production based upon the number of Units owned during each
      month of the year and apply the tax credit against his own

                                      -6-

<PAGE>   7

      income tax liability, but such credit may not reduce his regular tax
      liability (after the foreign tax credit and certain other nonrefundable
      credits) below his tentative minimum tax. Section 29 also provides that
      any amount of Section 29 credit disallowed for the tax year solely because
      of this limitation will increase his credit for prior year minimum tax
      liability, which may be carried forward indefinitely as a credit against
      the taxpayer's regular tax liability, subject, however, to the limitations
      described in the preceding sentence. There is no provision for the
      carryback or carryforward of the Section 29 credit in any other
      circumstances.

      The Trustee is provided summary Section 29 tax credit information related
      to Trust properties by BROG, which information is then passed along to the
      Unit holders. In Nielson-True Partnership, et al, v. Commissioner, a 1997
      Tax Court decision, the court ruled that nonconventional fuel (such as
      coal seam gas) produced from a well drilled and completed in an otherwise
      qualifying formation prior to December 31, 1992, is not eligible for the
      Section 29 credit unless the producer has received an appropriate well
      category determination from the Federal Energy Regulatory Commission
      ("FERC"). On March 23, 1999, the U. S. Court of Appeals for the 10th
      Circuit affirmed that decision. Dictum (i.e., language in the appeals
      court's decision which is not binding as precedent) even suggests that,
      contrary to the clear implications of a 1993 Internal Revenue Service
      ruling, lack of such a well category determination may render the Section
      29 credit unavailable in respect of production from wells recompleted in a
      qualified formation after January 1, 1993, the date that FERC's authority
      to render well category determinations ended (so that obtaining the
      requisite determination for any such well was impossible). Many producers
      assert that wells meeting the definitional requirements applied by FERC in
      rendering well category determinations are eligible for the Section 29
      credit regardless of whether a well category determination is actually
      applied for or received, particularly for wells recompleted in qualifying
      formations after January 1, 1993, and additional litigation (and perhaps a
      legislative initiative) on this issue is to be expected.

      In some cases the extent to which production from the various coal seam
      gas wells in which the Trust holds an interest would qualify for the
      Section 29 credit under the standards applied in the Nielson-True case is
      unclear, and the Trustee has requested that BROG provide clarification and
      an assessment of the effects of the foregoing, if any, on the Trust and
      its Unit holders. Pending such clarification and assessment, or further
      developments, or both, however, the availability of Section 29 credits to
      Unit holders in respect of some portion of the Trust's coal seam gas
      production could be subject to debate and challenge.

      The classification of the Trust's income for purposes of the passive loss
      rules may be important to a Unit holder. As a result of the Tax Reform Act
      of 1986, royalty income will generally be treated as portfolio income and
      will not reduce passive losses.

3.    CONTINGENCIES

      See Item 1 Legal Proceedings concerning the status of litigation matters.

                                     ******

                                      -7-

<PAGE>   8



ITEM 2.   TRUSTEE'S DISCUSSION AND ANALYSIS

FORWARD-LOOKING INFORMATION

Certain information included in this report contains, and other materials filed
or to be filed by the Trust with the Securities and Exchange Commission (as well
as information included in oral statements or other written statements made or
to be made by the Trust) may contain or include, forward-looking statements
within the meaning of Section 21E of the Securities Exchange Act of 1934, and
Section 27A of the Securities Act of 1933. Such forward looking statements may
be or may concern, among other things, capital expenditures, drilling activity,
development activities, production efforts and volumes, hydrocarbon prices and
the results thereof, and regulatory matters. Such forward looking statements
generally are accompanied by words such as "may," "will," "estimate," "expect,"
"predict," "anticipate," "goal," "should," "assume," "believe," "plan,"
"intend," or other words that convey the uncertainty of future events or
outcomes. Such statements reflect our current view with respect to future
events; are based on our assessment of, and are subject to, a variety of factors
deemed relevant by the Trustee and involve risks and uncertainties. Should one
or more of these risks or uncertainties occur, actual results may vary
materially and adversely from those anticipated.

YEAR 2000 ISSUE

Many existing computer programs use only two digits to identify a year in the
date field. These programs were designed and developed without considering the
impact of the upcoming change in the century. If not corrected, many computer
applications could fail or create erroneous results by or at January 1, 2000.
The Year 2000 issue affects virtually all companies and organizations. If a
company or organization does not successfully address its Year 2000 issues, it
may face material adverse consequences.

As the Trust does not directly maintain any systems, the Trust will not incur
any direct costs related to the Year 2000 issue. However, the Trust relies on
the performance of third parties, including the Trustee, BROG and third-party
vendors (collectively, the "suppliers") for such things as the calculation and
receipt of Royalty income, payment of expenses and disbursement of distributable
income. The Trustee has adopted an extensive and comprehensive testing plan to
help ensure that its systems will function properly before, during and after the
year 2000. The Trust has made formal inquiries of BROG and significant third
party vendors, including Harris Trust and Savings Bank, the transfer agent for
the Trust, to determine the extent to which the Trust is vulnerable to failure
by BROG or such other third parties to remediate their own Year 2000 issues.

BROG has informed the Trust that it has assessed its information technology for
Year 2000 issues. BROG's Year 2000 readiness plan involves four phases:
assessment, remediation, testing and implementation. BROG has completed all four
phases for all of its significant information technology. BROG has reported that
its assessment has confirmed that assets used in producing, gathering and
transporting hydrocarbons may be at risk of encountering Year 2000 problems, but
that information technology exposures were not material,. BROG further reports
that it has completed the remediation, testing and implementation phase for such
operation equipment with the goal of ensuring that all critical operating
equipment under its control remains operational. BROG has contacted all of its
third-party vendors that it considers material to its operations. All such
vendors have responded that they believe that Year 2000 issues will not have a
material adverse effect on their operations. BROG has surveyed the operators of
its three primary gathering and pipeline systems in the San Juan Basin,
including the operators that transport the gas gathered from the Underlying
Properties. BROG and other major producers in the San Juan Basin have developed
contingency plans to deal with unforeseen failures to information technology
with respect to these gathering and pipeline systems.

                                      -8-

<PAGE>   9



The Trust can provide no assurance as to whether BROG and third party vendors
will successfully address the Year 2000 issue. Failing to successfully address
the Year 2000 issue by BROG and third party vendors could have a material
adverse impact on the Trust and its Unit holders. At this time, the Trust
believes the most adverse impact that could result from the suppliers' failure
to successfully address the Year 2000 issue is the possibility that the Trust
would not receive, and in turn would not be able to distribute, Royalty income
to the Unit holders.

THREE MONTHS ENDED SEPTEMBER 30, 1999 AND SEPTEMBER 30, 1998:

The Trust received royalty income of $7,908,631 and interest income of $13,147
during the third quarter of 1999. After deducting administrative expenses of
$156,248 distributable income for the quarter was $7,765,530 ($.166611 per
Unit). In the third quarter of 1998, royalty income was $6,276,679, interest
income was $12,749, administrative expenses were $125,509 and distributable
income was $6,163,919 ($.132248 per Unit). The tax credit relating to production
from coal seam wells totaled approximately $.04 per Unit for the third quarter
of 1999 and $.04 per Unit for the third quarter of 1998. For further information
concerning this tax credit, Unit holders should refer to the Trust's Annual
Report for 1998. Based on 46,608,796 Units outstanding, the per Unit
distributions during the third quarter of 1999 were as follows:

<TABLE>

<S>                                                       <C>
                     July                                 $ .067887
                     August                                 .042463
                     September                              .056261
                                                          ---------

                     Quarter Total                        $ .166611
                                                          =========
</TABLE>


The royalty income distributed in the third quarter of 1999 was higher than that
distributed in the third quarter of 1998, primarily due to an increase in the
average gas price from $1.62 per Mcf for the third quarter of 1998 to $1.84 per
Mcf for the third quarter of 1999. Interest earnings for the quarter ended
September 30, 1999, as compared to the quarter ended September 30, 1998, were
higher, primarily due to an increase in funds available for investment.
Administrative expenses were higher, primarily as a result of differences in
timing of the receipt and payment of these expenses.

The capital costs attributable to the properties from which the Trust's 75% net
overriding royalty ("Royalty") was carved (the "Underlying Properties") for the
third quarter of 1999 were reported by BROG as $2,720,024 versus $3,745,082 for
the third quarter of 1998. BROG indicates that the majority of the decrease in
capital expenditures is attributable to the timing of payment of invoices
related to the 1999 infill program and a greater cost bearing interest
associated with 1998 capital workovers compared to 1999. BROG has recently
informed the Trustee that its estimated capital budget for 1999 has been
increased from $9.5 million to $11 million due to the reclassification of
charges for facility tubing change outs from an operating to a capital expense.
Lease operating expenses and property taxes decreased to $2,243,776 for the
third quarter of 1999 as compared to $2,786,500 for the third quarter of 1998.
BROG accrued $493,473 for January 1999 lease operating charges thought not to
have been processed. This accrual was reversed in August when it was determined
that the majority of such charges had in fact been processed. This reversal of
charges has caused lease operating expenses for the third quarter of 1999 to
appear lower than for the same period of 1998.

BROG has informed the Trustee that one gross (0.05 net) coal seam well was
completed as of September 30, 1999. One gross (0.88) net coal seam well, 19
gross (0.28 net) coal seam well recavitations, five gross (1.22 net) coal seam
recompletions, and 49 gross (11.81 net) conventional wells were in progress as
of September 30, 1999. By comparison, one gross (.04 net) conventional well was
completed on the Underlying Properties during the third quarter of 1998. There
were 36 gross (7.70 net) conventional wells in

                                      -9-

<PAGE>   10

progress at September 30, 1998. Two gross (1.47 net) conventional wells were
recompleted and five gross (.21 net) coal seam well recavitations were completed
on the Underlying Properties in the third quarter of 1998. Two gross (.07 net)
conventional well recompletions, one gross (.045 net) coal seam recompletion and
five gross (.16 net) coal seam recavitations were in progress at September 30,
1998. "Gross" acres or wells, for purposes of this discussion, means the entire
ownership interest of all parties in such properties, and BROG's interest
therein is referred to as the "net" acres or wells.

Royalty income for the quarter ended September 30, 1999 is associated with
actual gas and oil production during May 1999 through July 1999 from the
Underlying Properties. Gas and oil sales from the Underlying Properties for the
quarters ended September 30, 1999 and 1998 were as follows:

<TABLE>
<CAPTION>
                                                        1999            1998
<S>                                                  <C>             <C>
Gas:
   Total sales (Mcf)                                 9,253,207       10,135,621
   Mcf per day                                         100,578          110,170
   Average price (per Mcf)                          $     1.84      $      1.62

Oil:
   Total sales (Bbls)                                   18,837           18,478
   Bbls per day                                            205              201
   Average price (per Bbl)                          $    15.69      $     12.03
</TABLE>

Gas and oil sales attributable to the Royalty for the quarters ended September
30, 1999 and 1998 were as follows:

<TABLE>
<CAPTION>
                                                        1999             1998
<S>                                                  <C>              <C>
Gas sales (Mcf)                                      4,717,239        4,264,729
Oil sales (Bbls)                                         9,480            7,771
</TABLE>

Although gas sales attributable to the Royalty increased in the third quarter of
1999, as compared to the same period in 1998, interim reports received from BROG
indicated lower production for the months of June and July 1999, as compared to
the prior year. Upon inquiry from the Trust, BROG responded that the apparent
declines in gas production for those months did not reflect actual declines in
gas productivity, but rather, were the result of prior period adjustments. BROG
indicated that deficiencies in its new internal accounting system precluded it
from generating actual production reports for the months of January through
August, and it instead relied upon estimates based on historical production,
which estimates proved high. The prior period adjustments were employed by BROG
to reconcile the difference between its estimates and the actual production for
the subject months. The Trust's consultants have reviewed data supplied by BROG
in support of the prior period adjustments and have preliminarily approved them,
subject to final audit.

Since the oil and gas sales attributable to the Royalty are based on an
allocation formula that is dependent on such factors as price and cost,
including capital expenditures, the aggregate production volumes from the
Underlying Properties may not provide a meaningful comparison to volumes
attributable to the Royalty.

During the third quarter of 1999, gas prices were higher than during the third
quarter of 1998. Gas sales attributable to the Royalty increased slightly in
1999 as compared to 1998. The price per barrel of oil during the third quarter
of 1999 was $3.66 per bbl higher than that received for the third quarter of
1998 due to increases in oil prices in world markets generally including the
posted prices applicable to oil sales attributable to the Royalty.

                                      -10-

<PAGE>   11

Effective January 1, 1998, all volumes of gas which are subject to the Royalty
(the "Trust gas") became subject to the terms of a Natural Gas Sales and
Purchase Contract between BROG and El Paso Energy Marketing Company ("El Paso").
That contract is for a term of two years through and including December 31,
1999, and provides for the sale of Trust gas at prices which will fluctuate in
accordance with published indices for gas sold in the San Juan Basin of New
Mexico. BROG entered into the contract with El Paso after soliciting and
receiving competitive bids in late 1997 from six major gas marketing firms to
market and/or purchase the Trust gas. In August 1999 BROG distributed requests
for proposals to 19 gas marketing firms. Responses have been received and are
being reviewed and negotiated as part of the process of putting a successor
contract in place for marketing the Trust gas commencing January 1, 2000. Unit
holders are referred to Note 6 of the Notes to Financial Statements in the
Trust's 1998 Annual Report for further information concerning the marketing of
gas produced from the Underlying Properties.

In February 1999, the Trust's auditors notified the Trust of an apparent gas
imbalance. A gas imbalance occurs where more than one party is entitled to the
economic benefit of the production of natural gas, but the gas is sold for the
account of less than all of the parties. The resulting imbalance may be
corrected by various means including a cash settlement and/or a volume
adjustment whereby an increased percentage of future production is sold for the
account of the underproduced party or parties. The Trust's auditors suggested
that the subject imbalance might relate to the acquisition by BROG's
predecessor, Southland Royalty Company ("Southland Royalty"), of mineral
properties which had been operated under a Joint Operating Agreement between
Southland Royalty and Unicon, the seller of the properties. The Trust made
inquiry of BROG concerning the imbalance and BROG agreed to investigate the
records. The Trustee met with BROG representatives in June 1999 to discuss the
investigation and by correspondence of September 24, 1999, BROG reported that
the imbalance probably related to problems experienced in the 1980's and early
1990's by Southland Royalty and Unicon in their dealings with Public Service
Company of New Mexico. BROG reported that Unicon was flowing gas to its account
while Southland Royalty was not producing and that this created a gas imbalance.
The imbalance was addressed, as between Southland Royalty and Unicon, by a
reduction in the total purchase price for Unicon assets acquired by Southland
Royalty in June 1990. However, there was no payment made to the Trust at the
time of that acquisition.

BROG proposes to address the imbalance with the Trust based upon the terms of a
Gas Balancing Agreement it indicates was in place between Southland Royalty and
Unicon, in connection with the Joint Operating Agreement applicable to the
subject properties. BROG has offered $2,395,202.49 as a cash settlement. The
Trust is considering the appropriateness of this proposed resolution and this
offer and is consulting with its advisors. No assurance can be given as to when
and how this issue will be resolved or that the gas imbalance issue will be
resolved in favor of the Trust.

NINE MONTHS ENDED SEPTEMBER 30, 1999 AND 1998:

For the nine months ended September 30, 1999 distributable income was
$20,501,322 ($.439860 per Unit) which was less than the $24,012,820 ($.515199
per Unit) of income distributed during the same period in 1998. The Trust
received $892,496 as proceeds of a one-time business interruption insurance
claim as reported in the Trust's report on Form 10-Q for the quarter ended June
30, 1999. The decrease in distributable income resulted primarily from decreases
in gas and oil prices, partially offset by the one-time distribution of
insurance proceeds. Interest income for the nine months ended September 30, 1999
was $42,876 compared to $57,951 during the first nine months of 1998. This
decrease is due to a decrease in funds available for investment. General and
administrative expenses increased to $747,712 from $663,603 during the 1998
period primarily due to differences in timing of the receipt and payment of
these expenses.

Capital expenditures incurred by BROG, attributable to the Underlying
Properties, for the first nine months of 1999 amounted to $7,991,065. Capital
expenditures were $10,048,169 for the first nine months of 1998.

                                      -11-

<PAGE>   12

Lease operating expenses and property taxes totaled $7,888,702 for the first
nine months of 1999 compared to $8,590,061 for the first nine months of 1998.

BROG advised the Trustee that during the nine months ended September 30, 1999,
22 gross (.401 net) conventional wells were completed on the Underlying
Properties. One gross (.05 net) coal seam well was completed. Twelve gross (.144
net) coal seam wells were recavitated during the first six months of 1999.
During the nine months ended September 30, 1998, ten gross (5.13 net)
conventional gas wells were completed on the Underlying Properties and 21 gross
(10.74 net) conventional wells were recompleted. Twenty-nine gross (2.01 net)
coal seam wells were recavitated during the first nine months of 1998.

Royalty income for the nine months ended September 30, 1999 is associated with
actual gas and oil production during November 1998 through July 1999 from the
Underlying Properties. Gas and oil sales from the Underlying Properties for the
nine months ended September 30, 1999 and 1998 were as follows:

<TABLE>
<CAPTION>
                                                        1999            1998
<S>                                                 <C>              <C>
Gas:
   Total sales (Mcf)                                30,124,323       31,263,993
   Mcf per day                                         110,346          114,520
   Average price (per Mcf)                         $      1.56      $      1.81

Oil:
   Total sales (Bbls)                                   55,357           63,694
   Bbls per day                                            203              233
   Average price (per Bbl)                         $     12.69      $     13.80
</TABLE>

Gas and oil sales attributable to the Royalty for the nine months ended
September 30, 1999 and 1998 were as follows:

<TABLE>
<CAPTION>
                                                         1999            1998
<S>                                                 <C>              <C>
Gas sales (Mcf)                                     14,153,839       14,721,489
Oil sales (Bbls)                                        26,096           29,706
</TABLE>

During the first nine months of 1999, gas and oil prices were lower than during
the first nine months of 1998. Since the oil and gas sales attributable to the
Royalty are based on an allocation formula that is dependent on such factors as
price and cost, including capital expenditures, the aggregate sales amounts from
the Underlying Properties may not provide a meaningful comparison to sales
attributable to the Royalty.

                                      -12-

<PAGE>   13

CALCULATION OF ROYALTY INCOME:

Royalty income received by the Trust for the three months and nine months ended
September 30, 1999 and 1998, respectively, was computed as shown in the
following table:

<TABLE>
<CAPTION>

                                             THREE MONTHS ENDED            NINE MONTHS ENDED
                                               SEPTEMBER 30,                 SEPTEMBER 30,
                                        ---------------------------   ----------------------------
                                            1999           1998           1999           1998
<S>                                     <C>            <C>            <C>             <C>
Gross proceeds of sales from
   the Underlying Properties :

   Gas proceeds                         $ 17,003,534   $ 16,436,207   $ 47,093,562    $ 56,513,251
   Oil proceeds                              296,092        222,230        702,209         879,060
                                        ------------   ------------   ------------    ------------

           Total                          17,299,626     16,658,437     47,795,771      57,392,311
                                        ------------   ------------   ------------    ------------

Less production costs:
   Severance tax - Gas                     1,756,659      1,735,847      4,853,720       5,832,736
   Severance tax - Oil                        34,325         22,103         72,846          96,716
   Lease operating expenses
      and property tax                     2,243,776      2,786,500      7,888,702       8,590,061
   Capital expenditures                    2,720,024      3,745,082      7,991,065      10,048,169
   Other (a)                                    --             --          (95,445)           --
                                        ------------   ------------   ------------    ------------

           Total                           6,754,784      8,289,532     20,710,888      24,567,682
                                        ------------   ------------   ------------    ------------

Net profits                               10,544,842      8,368,905     27,084,883      32,824,629
                                        ------------   ------------   ------------    ------------

Net overriding royalty
   interest                                       75%            75%            75%             75%
                                        ------------   ------------   ------------    ------------

Royalty income                          $  7,908,632   $  6,276,679   $ 20,313,662    $ 24,618,472
                                        ============   ============   ============    ============
</TABLE>

(a) represents the payment of interest for the late payment of gas revenue


ITEM 3.    QUALITATIVE AND QUANTITATIVE DISCLOSURES ABOUT MARKET RISK

The Trust has not entered into derivative financial instruments, derivative
commodity instruments or other similar instruments during the quarter ended
September 30, 1999. The Trust does not market the Trust gas, oil and/or natural
gas liquids. BROG is responsible for such marketing.

                                      -13-

<PAGE>   14



                           PART II - OTHER INFORMATION

Item 1.         Legal Proceedings

                The Trust is not a party to any litigation. However, the Trust
                is aware that BROG is involved in litigation from time to time
                that could affect the royalty income received by the Trust.

                A lawsuit was commenced on September 1, 1995 against BROG by
                certain royalty and overriding royalty owners on behalf of those
                persons similarly situated. The suit involves properties that
                are burdened by the Trust. This case is one of six virtually
                identical class actions filed against New Mexico gas producers.
                All such cases have been consolidated in the First Judicial
                District of Santa Fe County, New Mexico where the case is styled
                San Juan 1990-A, L.P., et al. v. El Paso Production Company and
                Meridian Oil Inc. The plaintiffs allege that they and members of
                the proposed class have been underpaid for royalties and
                overriding royalties. The plaintiffs have sought to certify the
                actions as class actions and seek monetary damages. The court
                has denied class certification, but the plaintiffs have renewed
                their request for class certification. Discovery in this matter
                is said to be near conclusion, and BROG anticipates summary
                judgment proceedings to occur in the fall of 1999. Because of
                the pending nature of the litigation, exposure to the Trust from
                this suit cannot be quantified. However, if the plaintiffs who
                have interests in properties that are burdened by the Trust are
                successful, royalty income received by the Trust could decrease.

                In addition, an administrative claim was initiated on March 17,
                1997 by the Mineral Management Service of the United States
                Department of the Interior (the "MMS") against BROG regarding a
                gas contract settlement dated March 1, 1990, between BROG and
                certain other parties thereto. The claim alleges that additional
                royalties are due on production from federal and Indian leases
                in the State of New Mexico on properties that are burdened by
                the Royalty. In June 1997 BROG filed its statement of reasons
                thereby contesting whether the royalties are payable as claimed.
                BROG has informed the Trust that the administrative claim is in
                the appeal process. If the MMS claim is successful, royalty
                income received by the Trust could decrease.

                BROG is in negotiations with the State of New Mexico for a tax
                refund based upon a claim for reimbursement of compression costs
                used in calculating wellhead values. BROG has obtained the
                approval of the Attorney General of New Mexico of a settlement
                in the amount of $4,200,000, but no payment has yet been
                received. BROG has not informed the Trust of the proportion of
                the settlement proceeds, which will be attributable to the
                Trust.

Item 5.         Other

                In February 1999, the Trust's auditors notified the Trust of an
                apparent gas imbalance. A gas imbalance occurs where more than
                one party is entitled to the economic benefit of the production
                of natural gas, but the gas is sold for the account of less than
                all of the parties. The resulting imbalance may be corrected by
                various means including a cash settlement and/or a volume
                adjustment whereby an increased percentage of future production
                is sold for the account of the underproduced party or parties.
                The Trust's auditors suggested that the subject imbalance might
                relate to the acquisition by BROG's predecessor, Southland
                Royalty Company ("Southland Royalty"), of mineral properties
                which had been operated under a Joint Operating Agreement
                between Southland Royalty and Unicon, the seller of the
                properties. The Trust made inquiry of BROG concerning the
                imbalance and BROG agreed to investigate the records. The
                Trustee met with BROG representatives in June 1999 to discuss
                the investigation, and by correspondence of September 24, 1999,
                BROG reported that the imbalance probably related to
                problems experienced in the 1980's

                                      -14-

<PAGE>   15

                and early 1990's by Southland Royalty and Unicon in their
                dealings with Public Service Company of New Mexico. BROG
                reported that Unicon was flowing gas to its account while
                Southland Royalty was not producing and that this created a
                gas imbalance. The imbalance was addressed, as between
                Southland Royalty and Unicon, by a reduction in the total
                purchase price for Unicon assets acquired by Southland Royalty
                in June 1990. However, there was no payment made to the Trust
                at the time of that acquisition.

                BROG proposes to address the imbalance with the Trust based upon
                the terms of a Gas Balancing Agreement it indicates was in place
                between Southland Royalty and Unicon, in connection with the
                Joint Operating Agreement applicable to the subject properties
                and has offered $2,395,202.49 as a cash settlement. The Trust is
                considering the appropriateness of this proposed means of
                resolution and this offer and is consulting with its advisors.
                No assurance can be given as to when and how this issue will be
                resolved.

Item 6.         Exhibits and Reports on Form 8-K

                (a)  Exhibits

                     (4)(a)  San Juan Basin Royalty Trust Indenture dated
                             November 3, 1980, between Southland Royalty Company
                             (now Burlington Resources Oil & Gas Company) and
                             The Fort Worth National Bank (now Bank One, Texas,
                             N.A.), as Trustee, heretofore filed as Exhibit
                             (4)(a) to the Trust's Annual Report on Form 10-K to
                             the Securities and Exchange Commission for the
                             fiscal year ended December 31, 1980 is incorporated
                             herein by reference.

                     (4)(b)  Net Overriding Royalty Conveyance from Southland
                             Royalty Company (now Burlington Resources Oil & Gas
                             Company) to The Fort Worth National Bank (now Bank
                             One, Texas, N.A.), as Trustee, dated November 3,
                             1980 (without Schedules), heretofore filed as
                             Exhibit (4)(b) to the Trust's Annual Report on Form
                             10-K to the Securities and Exchange Commission for
                             the fiscal year ended December 31, 1980 is
                             incorporated herein by reference.

                     (27)    Financial Data Schedule

                (b)  Reports on Form 8-K

                     No reports on Form 8-K were filed during the quarter ended
September 30, 1999.

                                      -15-

<PAGE>   16



                                   SIGNATURES


Pursuant to the requirements of the Securities Exchange Act of 1934, the
Registrant has duly caused this Report to be signed on its behalf by the
undersigned thereunto duly authorized.

                                           BANK ONE, TEXAS, N.A., AS TRUSTEE FOR
                                           THE SAN JUAN BASIN ROYALTY TRUST



                                                 By /s/ LEE ANN ANDERSON
                                                    ---------------------------
                                                         Lee Ann Anderson
                                                          Vice President

Date:  November 12, 1999


               (The Trust has no directors or executive officers.)





                                      -16-

<PAGE>   17




                                INDEX TO EXHIBITS

<TABLE>
<CAPTION>
                                                                                               SEQUENTIALLY
               EXHIBIT                                                                           NUMBERED
               NUMBER                        EXHIBIT                                               PAGE
<S>                       <C>                                                             <C>
               (4)(a)     San Juan Basin Royalty Trust Indenture dated November
                          3, 1980, between Southland Royalty Company (now
                          Burlington Resources Oil & Gas Company) and The Fort
                          Worth National Bank (now Bank One, Texas, N.A.), as
                          Trustee, heretofore filed as Exhibit (4)(a) to the
                          Trust's Annual Report on Form 10 K to the Securities
                          and Exchange Commission for the fiscal year ended
                          December 31, 1980 is incorporated herein by
                          reference.*


               (4)(b)     Net Overriding Royalty Conveyance from Southland
                          Royalty Company (now Burlington Resources Oil & Gas
                          Company) to The Fort Worth National Bank (now Bank
                          One, Texas, N.A.), as Trustee, dated November 3, 1980
                          (without Schedules), heretofore filed as Exhibit
                          (4)(b) to the Trust's Annual Report on Form 10-K to
                          the Securities and Exchange Commission for the fiscal
                          year ended December 31, 1980 is incorporated herein by
                          reference.*

               (27)       Financial Data Schedule **
</TABLE>


*    A copy of this Exhibit is available to any Unit holder, at the actual cost
     of reproduction, upon written request to the Trustee, Bank One, Texas,
     N.A., P.O. Box 2604, Fort Worth, Texas 76113.

**   Filed herewith.