<PAGE>
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                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549
 
                            ------------------------
 
                                   FORM 10-Q
 
(MARK ONE)
 
  /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,
                                       OR
 
  / /    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 333-41121
 
                            ------------------------
 
                          FIRST CONSULTING GROUP, INC.
             (Exact name of registrant as specified in its charter)
 
                  DELAWARE                             95-3539020
      (State or other jurisdiction of        (I.R.S. Employer Identification
       incorporation or organization)                     No.)
 
               111 W. OCEAN BLVD. 4TH FLOOR, LONG BEACH, CA 90802
          (Address of principal executive offices including zip code)
 
                                 (562) 624-5200
 
              (Registrant's telephone number, including area code)
 
                            ------------------------
 
   (Former name, former address and former fiscal year, if changed since last
                                    report)
 
    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 (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 / /
 
    Indicate the number of shares outstanding of each of the issuer's classes of
common stock, as of the latest practicable date.
 
<TABLE>
<S>                                            <C>
        COMMON STOCK, $.001 PAR VALUE                        16,002,217 SHARES
--------------------------------------------   --------------------------------------------
                   (Class)                          (Outstanding at September 30, 1998)
</TABLE>
 
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<PAGE>
                          FIRST CONSULTING GROUP, INC.
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                                                                                               PAGE
                                                                                                              NUMBER
                                                                                                           -------------
<S>          <C>         <C>                                                                               <C>
COVER PAGE ..............................................................................................            1
 
TABLE OF CONTENTS .......................................................................................            2
 
PART I.      FINANCIAL INFORMATION ......................................................................            3
 
             ITEM 1.     FINANCIAL STATEMENTS AND NOTES (UNAUDITED)......................................            3
 
                         Consolidated Balance Sheets as of September 30, 1998 and December 31, 1997......            3
 
                         Consolidated Statements of Operations for the three month periods ended
                           September 30, 1998 and September 30, 1997, and nine month periods ended
                           September 30, 1998 and September 30, 1997.....................................            5
 
                         Condensed Consolidated Statements of Cash Flows for the nine month periods ended
                           September 30, 1998 and September 30, 1997.....................................            6
 
                         Notes to Consolidated Financial Statements......................................            7
 
             ITEM 2.     MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF
                           OPERATIONS....................................................................            9
 
PART II.     OTHER INFORMATION ..........................................................................           13
 
             ITEM 1.     LEGAL PROCEEDINGS...............................................................           13
 
             ITEM 2.     CHANGES IN SECURITIES...........................................................           13
 
             ITEM 3.     DEFAULTS UPON SENIOR SECURITIES.................................................           13
 
             ITEM 4.     SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS.............................           13
 
             ITEM 5.     OTHER INFORMATION...............................................................           13
 
             ITEM 6.     EXHIBITS AND REPORTS ON FORM 8-K................................................           13
 
SIGNATURES ..............................................................................................           14
 
EXHIBIT INDEX
</TABLE>
 
                                       2
<PAGE>
                         PART I. FINANCIAL INFORMATION
 
ITEM 1. FINANCIAL STATEMENTS AND NOTES (UNAUDITED).
 
                 FIRST CONSULTING GROUP, INC. AND SUBSIDIARIES
 
                    CONSOLIDATED BALANCE SHEETS (UNAUDITED)
                                 (IN THOUSANDS)
                                     ASSETS
 
<TABLE>
<CAPTION>
                                                                       SEPTEMBER    DECEMBER
                                                                          30,          31,
                                                                         1998         1997
                                                                      -----------  -----------
                                                                      (UNAUDITED)
<S>                                                                   <C>          <C>
Current assets
  Cash and cash equivalents.........................................   $  13,485    $   2,950
  Investments available for sale....................................      11,130       --
  Accounts receivable, less allowance of $500.......................      23,842       11,846
  Work in process...................................................      11,352        8,030
  Prepaid expenses..................................................       1,821          821
  Income tax receivables............................................         132        1,114
  Current portion of notes receivable--stockholders.................      --              328
                                                                      -----------  -----------
    Total current assets............................................      61,762       25,089
Notes receivable--stockholders......................................       1,772        1,368
Property and equipment
  Furniture, equipment, and leasehold improvements..................       2,443        1,874
  Information systems equipment.....................................      11,822        9,040
                                                                      -----------  -----------
                                                                          14,265       10,914
Less accumulated depreciation and amortization......................       7,941        5,641
                                                                      -----------  -----------
                                                                           6,324        5,273
 
Other assets
  Executive benefit trust...........................................       3,511        2,506
  Long-term investments.............................................      25,758       --
  Goodwill..........................................................       1,193       --
  Other.............................................................         511          189
                                                                      -----------  -----------
                                                                          30,973        2,695
                                                                      -----------  -----------
    Total assets....................................................   $ 100,831    $  34,425
                                                                      -----------  -----------
                                                                      -----------  -----------
</TABLE>
 
                            See accompanying notes.
 
                                       3
<PAGE>
                 FIRST CONSULTING GROUP, INC. AND SUBSIDIARIES
 
                    CONSOLIDATED BALANCE SHEETS (CONTINUED)
                                 (IN THOUSANDS)
                      LIABILITIES AND STOCKHOLDERS' EQUITY
 
<TABLE>
<CAPTION>
                                                                       SEPTEMBER    DECEMBER
                                                                          30,          31,
                                                                         1998         1997
                                                                      -----------  -----------
                                                                      (UNAUDITED)
<S>                                                                   <C>          <C>
Current liabilities
  Line of credit....................................................   $  --        $   2,000
  Current portion of long-term debt.................................         228          871
  Accounts payable..................................................       2,496          735
  Accrued liabilities...............................................      10,879        2,219
  Accrued vacation..................................................       2,684        1,923
  Deferred revenue..................................................         377          391
  Customer advances.................................................       2,296        1,965
  Current income tax liability......................................       4,663       --
  Deferred income taxes.............................................       6,503        5,679
                                                                      -----------  -----------
    Total current liabilities.......................................      30,126       15,783
Non-current liabilities
  Long-term debt, net of current portion............................         209          262
  Supplemental executive retirement plan............................       3,501        2,506
  Deferred income taxes.............................................         447          447
                                                                      -----------  -----------
                                                                           4,157        3,215
Commitments and contingencies.......................................      --           --
Put obligation related to Associate 401(k) and Stock Ownership Plan
  (ASOP) and capital stock..........................................      --            9,965
Stockholders' equity
  Preferred Stock, 10,000,000 shares authorized, no shares issued
    and outstanding.................................................      --           --
  Common Stock, 50,000,000 shares authorized, 16,002,217 shares
    issued and outstanding at September 30, 1998 and 12,042,664
    shares issued and outstanding at December 31, 1997..............          16           12
  Additional paid-in capital........................................      68,256       20,822
  Retained earnings.................................................      10,111        4,215
  Deferred compensation--stock incentive agreements.................      (4,077)      (3,635)
  Unearned ASOP shares..............................................        (853)        (853)
  Notes receivable--stockholders....................................      (6,905)      (5,134)
  Put obligation related to ASOP and capital stock..................      --           (9,965)
    Total stockholders' equity......................................      66,548        5,462
                                                                      -----------  -----------
    Total liabilities and stockholders' equity......................   $ 100,831    $  34,425
                                                                      -----------  -----------
                                                                      -----------  -----------
</TABLE>
 
                            See accompanying notes.
 
                                       4
<PAGE>
                 FIRST CONSULTING GROUP, INC. AND SUBSIDIARIES
 
               CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED)
                     (IN THOUSANDS, EXCEPT PER SHARE DATA)
 
<TABLE>
<CAPTION>
                                               THREE MONTHS ENDED        NINE MONTHS ENDED
                                            ------------------------  ------------------------
                                             SEPTEMBER    SEPTEMBER    SEPTEMBER    SEPTEMBER
                                                30,          30,          30,          30,
                                               1998         1997         1998         1997
                                            -----------  -----------  -----------  -----------
<S>                                         <C>          <C>          <C>          <C>
Net revenue...............................   $  34,215    $  24,477    $  94,601    $  66,305
Cost of services..........................      18,427       14,098       51,813       38,823
                                            -----------  -----------  -----------  -----------
  Gross profit............................      15,788       10,379       42,788       27,482
General and administrative expenses.......      12,078        8,648       32,815       22,804
Compensation expenses related to stock
  issuances...............................      --              815       --            1,861
                                            -----------  -----------  -----------  -----------
  Income from operations..................       3,710          916        9,973        2,817
Other income
  Interest income (expense), net..........         528          (11)       1,325          (59)
  Other income, net.......................          13            9           48          110
                                            -----------  -----------  -----------  -----------
    Income before income taxes............       4,251          914       11,346        2,868
Provision for income taxes................       2,058          507        5,449        1,590
                                            -----------  -----------  -----------  -----------
    Net income............................   $   2,193    $     407    $   5,897    $   1,278
                                            -----------  -----------  -----------  -----------
                                            -----------  -----------  -----------  -----------
Basic net income per share................   $   0.140    $   0.041    $   0.393    $   0.132
Diluted net income per share..............   $   0.134    $   0.039    $   0.375    $   0.124
Shares used in computing basic net income
  per share...............................      15,662        9,975       15,001        9,687
Shares used in computing diluted net
  income per share........................      16,421       10,513       15,722       10,279
</TABLE>
 
                            See accompanying notes.
 
                                       5
<PAGE>
                 FIRST CONSULTING GROUP, INC. AND SUBSIDIARIES
 
          CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)
                                 (IN THOUSANDS)
 
<TABLE>
<CAPTION>
                                                                         NINE MONTHS ENDED
                                                                     --------------------------
                                                                      SEPTEMBER
                                                                         30,      SEPTEMBER 30,
                                                                        1998          1997
                                                                     -----------  -------------
<S>                                                                  <C>          <C>
Cash flows from operating activities:
  Net income.......................................................   $   5,897     $   1,278
  Net noncash charges to income....................................       2,300         6,195
  Change in operating assets and liabilities.......................        (650)        2,473
                                                                     -----------       ------
    Net cash provided by operating activities......................       7,547         9,946
                                                                     -----------       ------
Cash flows from investing activities:
Purchase of investments............................................     (36,796)       --
  Furniture, equipment, and leasehold improvements.................        (569)         (678)
  Information systems equipment....................................      (2,782)       (1,726)
  Notes receivable stockholders....................................      (1,808)       (2,922)
                                                                     -----------       ------
    Net cash used in investing activities..........................     (41,955)       (5,326)
                                                                     -----------       ------
Cash flows used in financing activities:
  Long-term debt...................................................         (53)         (246)
  Line of credit...................................................      (2,000)       --
  Proceeds from issuance of stock..................................      47,438           155
  Deferred compensation stock incentive............................        (442)         (305)
                                                                     -----------       ------
    Net cash generated in financing activities.....................      44,943          (396)
                                                                     -----------       ------
Net increase (decrease) in cash and equivalents....................      10,535         4,224
Cash and equivalents at beginning of period........................       2,950           214
                                                                     -----------       ------
Cash and equivalents at end of period..............................   $  13,485     $   4,438
                                                                     -----------       ------
                                                                     -----------       ------
</TABLE>
 
                            See accompanying notes.
 
                                       6
<PAGE>
                 FIRST CONSULTING GROUP, INC. AND SUBSIDIARIES
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
 
1. BASIS OF PRESENTATION
 
    The consolidated balance sheets of First Consulting Group, Inc. (the
"Company") at September 30, 1998 and consolidated statements of operations and
condensed consolidated statements of cash flows for the periods ended September
30, 1998 and 1997 are unaudited. These financial statements reflect all
adjustments, consisting of only normal recurring adjustments, which, in the
opinion of management, are necessary to fairly present the financial position of
the Company at September 30, 1998 and the results of operations for the
three-month periods ended September 30, 1998 and September 30, 1997, and the
nine-month periods ended September 30, 1998 and September 30, 1997. The results
of operations for the nine months ended September 30, 1998 are not necessarily
indicative of the results to be expected for the year ending December 31, 1998.
For more complete financial information, these financial statements should be
read in conjunction with the audited financial statements for the year ended
December 31, 1997 included in the Company's Registration Statement on Form S-1,
File No. 333-41121, declared effective on February 12, 1998.
 
2. STOCKHOLDERS' EQUITY
 
    On November 25, 1997, a certificate of incorporation was filed with the
state of Delaware forming First Consulting Group, Inc. and authorizing
50,000,000 shares of common stock and authorizing 10,000,000 shares of preferred
stock. On January 22, 1998, the Board of Directors of FCG Enterprises, Inc., a
California company, approved a 4-for-1 split of common stock in the form of a
stock dividend. On February 10, 1998, FCG Enterprises, Inc., a California
company, merged into First Consulting Group, Inc., a Delaware company. On
February 13, 1998, First Consulting Group, Inc., completed an initial public
offering of its common stock in which 3,801,858 shares of common stock were sold
by the Company, resulting in net proceeds of approximately $45.1 million; an
additional 812,384 shares of common stock were sold by existing stockholders.
 
3. INVESTMENTS
 
    For purposes of reporting cash flows, cash and cash equivalents include cash
and interest-earning deposits or securities with original maturities of three
months or less. The Company has approximately $11.1 million in short term
investments and $25.8 million in non-current investments classified as available
for sale. Such investments are currently held primarily in tax-exempt government
securities. Net unrealized gains and losses on investments were not material at
September 30, 1998.
 
4. RECENT DEVELOPMENTS
 
    On September 9, 1998, the Company signed a definitive merger agreement and
plan of reorganization for the acquisition of Integrated Systems Consulting
Group, Inc. (ISCG), a leading provider of application development, document
management and network integration services predominately for the pharmaceutical
industry. The Company expects this transaction to close during the fourth
quarter of 1998. After such time, the financial condition and results of
operations of the two companies will be reported on a combined basis.
 
    Under the terms of the agreement, each outstanding share of ISCG common
stock will be exchanged at a fixed exchange rate of 0.77 for a newly issued
share of Company common stock. The transaction is intended to be accounted for
as a pooling-of-interests and is intended to qualify as a tax-free
reorganization. Shareholders representing approximately 56.6% and 27% of the
common stock outstanding of ISCG and the Company respectively have signed
irrevocable proxies to vote in favor of the merger.
 
                                       7
<PAGE>
                 FIRST CONSULTING GROUP, INC. AND SUBSIDIARIES
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)
 
5. NET INCOME PER SHARE
 
    The following represents a reconciliation of basic and diluted net income
per share for the three month and nine month periods ended September 30, 1998
and 1997, respectively (amounts rounded to thousands, except per share data):
 
<TABLE>
<CAPTION>
                                                                  FOR THE THREE MONTHS ENDED     FOR THE THREE MONTHS ENDED
                                                                      SEPTEMBER 30, 1998             SEPTEMBER 30, 1997
                                                                 ----------------------------   -----------------------------
                                                                         WEIGHTED                        WEIGHTED
                                                                         AVERAGE    PER SHARE            AVERAGE    PER SHARE
                                                                 INCOME   SHARES     AMOUNT     INCOME    SHARES     AMOUNT
                                                                 ------  --------   ---------   ------   --------   ---------
<S>                                                              <C>     <C>        <C>         <C>      <C>        <C>
Basic EPS:
  Income available to common stockholders......................  $2,193   15,662     $0.140      $407      9,975     $0.041
                                                                                    ---------                       ---------
                                                                                    ---------                       ---------
Effect of dilutive securities:
  Options:.....................................................    --        759                 --          538
                                                                 ------  --------               ------   --------
 
Diluted EPS:
  Income available to common stockholders and assumed
    conversions................................................  $2,193   16,421     $0.134      $407     10,513     $0.039
                                                                 ------  --------   ---------   ------   --------   ---------
                                                                 ------  --------   ---------   ------   --------   ---------
</TABLE>
 
<TABLE>
<CAPTION>
                                                                 FOR THE NINE MONTHS ENDED      FOR THE NINE MONTHS ENDED
                                                                     SEPTEMBER 30, 1998             SEPTEMBER 30, 1997
                                                                ----------------------------   ----------------------------
                                                                        WEIGHTED                       WEIGHTED
                                                                        AVERAGE    PER SHARE           AVERAGE    PER SHARE
                                                                INCOME   SHARES     AMOUNT     INCOME   SHARES     AMOUNT
                                                                ------  --------   ---------   ------  --------   ---------
<S>                                                             <C>     <C>        <C>         <C>     <C>        <C>
Basic EPS:
  Income available to common stockholders.....................  $5,897   15,001     $0.393     $1,278    9,687     $0.132
                                                                                   ---------                      ---------
                                                                                   ---------                      ---------
Effect of dilutive securities:
  Options:....................................................    --        721                  --        592
                                                                ------  --------               ------  --------
 
Diluted EPS:
Income available to common stockholders and assumed
  conversions.................................................  $5,897   15,722     $0.375     $1,278   10,279     $0.124
                                                                ------  --------   ---------   ------  --------   ---------
                                                                ------  --------   ---------   ------  --------   ---------
</TABLE>
 
                                       8
<PAGE>
ITEM 2. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND
RESULTS OF OPERATIONS
 
    THE FOLLOWING MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION
AND RESULTS OF OPERATIONS CONTAINS FORWARD-LOOKING STATEMENTS WITHIN THE MEANING
OF THE PRIVATE SECURITIES LITIGATION REFORM ACT OF 1995. SUCH FORWARD LOOKING
STATEMENTS INVOLVE RISKS AND UNCERTAINTIES, INCLUDING THOSE SET FORTH HEREIN AND
UNDER THE CAPTION "RISK FACTORS" IN THE COMPANY'S REGISTRATION STATEMENT ON FORM
S-1, FILE NO. 333-41121, DECLARED EFFECTIVE ON FEBRUARY 12, 1998. THE COMPANY'S
ACTUAL RESULTS COULD DIFFER MATERIALLY FROM THOSE ANTICIPATED IN THESE
FORWARD-LOOKING STATEMENTS.
 
OVERVIEW
 
    FCG provides consulting, implementation, integration and management services
to payors, providers and other healthcare organizations in North America and
Europe. The Company's services are designed to increase its clients' operations
effectiveness in order to reduce cost, improve customer service and enhance the
quality of patient care. The Company's services address the increasing need of
its clients for healthcare-specific information technology expertise to
objectively evaluate, select, implement and manage an optimal set of information
systems and infrastructures. The Company's consultants provide this expertise
through multi-disciplinary teams specifically formed to provide a unique
solution for each client. The Company believes that its success is attributable
to its strong relationships with industry-leading clients, the healthcare,
technology and consulting expertise of the Company's consultants, and the depth
and breadth of its consulting services.
 
    The Company generates substantially all of its revenue from fees for
professional services. The Company typically bills for its services on an
hourly, fixed-fee or fixed-fee per month basis as specified by the agreement
with a particular client. The Company establishes standard hourly rates for each
level of consultant based on several factors including industry and
assignment-related experience, technical expertise, skills and knowledge. For
services billed on an hourly basis, fees are determined by multiplying the
amount of time expended on each assignment by the hourly rate for the
consultant(s) assigned to the engagement. Fixed fees are established on a
per-assignment or monthly basis and are based on several factors such as the
size, scope, complexity and duration of an assignment and the number of
consultants required to complete the assignment. Actual hourly or fixed fees for
an assignment may vary from the standard or historical rates charged by the
Company. For services billed on an hourly basis, the Company recognizes revenue
as services are performed. For services billed on a fixed fee basis, the Company
recognizes revenue using the percentage of completion method based on the amount
of time completed on each assignment versus the projected number of hours
required to complete such assignment. Revenue is recorded as incurred at
assignment rates net of unplanned adjustments for specific engagements.
Unplanned adjustments to revenue are booked at the time they are known. The
Company may obtain payment in advance of providing services. These advances are
recorded as deferred revenue and reflected as a liability on the Company's
balance sheet.
 
    Cost of services primarily consists of the salaries, bonuses and related
benefits of consultants, subcontractor expenses, and the costs of the Company's
supplemental executive retirement plan. General and administrative expenses
primarily consist of the costs attributable to office space occupancy;
investments in the Company's information systems, research and practice support
and quality initiatives; salaries and expenses for executive management,
financial accounting and administrative personnel; recruiting fees and
professional development; and marketing, legal and other professional services.
 
    In connection with the Company's Associate 401(k) and Stock Ownership Plan
("ASOP") and certain non-qualified stock options granted to the Company's vice
presidents, the Company recognizes a compensation expense on its consolidated
statement of operations. The recurring portion of the Company's
 
                                       9
<PAGE>
compensation expense relating to stock issuances and the amortization of
deferred compensation is reflected in the Company's consolidated statements of
operations as general and administrative expenses or cost of services based on
the function of the employee to whom the charge relates. Beginning in 1998, the
Company has granted all stock options at fair market value and, in connection
with the Company's ASOP, matches employee 401(k) contributions with shares of
Common Stock based on the fair market value of the shares.
 
    The Company's most significant expenses are its human resource-related
salary and benefit expenses. As of September 30, 1998, approximately 80% of the
Company's 774 employees are consultants, and the salaries and benefits of such
consultants are recognized in the Company's cost of services. Non-billable
employee salaries and benefits are recognized as a component of general and
administrative expenses. The Company's cost of services as a percentage of
revenue is directly related to its consultant utilization, which is the ratio of
total billable hours to available hours in a given month. The Company manages
consultant utilization by monitoring assignment requirements and timetables,
available and required skills, and available consultant hours per week and per
month. The number of consultants staffed on an assignment will vary according to
the size, complexity, duration and demands of the assignment. Assignment
terminations, completions and scheduling delays may result in periods in which
consultants are not optimally utilized. An unanticipated termination of a
significant assignment or an overall lengthening of the sales cycle could result
in a higher than expected number of unassigned consultants and could cause the
Company to experience lower margins. In addition, the opening of new offices,
expansion into new markets, and the hiring of consultants in advance of client
assignments have resulted and may continue to result in periods of lower
consultant utilization.
 
    The Company's effective tax rate has varied from period to period due to
non-deductible losses from the Company's foreign operations and differences
between book and tax deductions associated with certain non-deductible operating
expenses, including certain compensation expenses related to the ASOP.
 
RESULTS OF OPERATIONS FOR THE THREE MONTHS ENDED SEPTEMBER 30, 1998 AND 1997
 
    NET REVENUE.  The Company's net revenue increased to $34.2 million, or
39.8%, for the quarter ended September 30, 1998 from $24.5 million for the
quarter ended September 30, 1997. This increase was primarily attributable to an
increase in revenue from the Company's implementation, operations effectiveness,
and integration services.
 
    COST OF SERVICES.  Cost of services increased to $18.4 million, or 30.7%,
for the quarter ended September 30, 1998 from $14.1 million for the quarter
ended September 30, 1997. The increase was primarily attributable to an increase
in the number of consultants. Cost of services as a percentage of revenue
decreased to 53.9% for the quarter ended September 30, 1998 from 57.6% for the
quarter ended September 30, 1997. This decrease was primarily attributable to
increased realization of standard fees during the quarter ended September 30,
1998.
 
    GENERAL AND ADMINISTRATIVE EXPENSES.  General and administrative expenses
increased to $12.1 million, or 39.7%, for the quarter ended September 30, 1998
from $8.6 million for the quarter ended September 30, 1997. General and
administrative expenses as a percentage of revenue remained consistent at 35.3%
for both quarters.
 
    COMPENSATION EXPENSES RELATED TO STOCK ISSUANCES.  Compensation expenses
related to stock issuances decreased to zero for the quarter September 30, 1998
from $815,000 and for the quarter ended September 30, 1997. This decrease was
attributable to the discontinuance of certain compensatory stock and option
issuances.
 
    INTEREST INCOME, NET.  Interest income, net of interest expense, increased
to $528,000 for the quarter ended September 30, 1998 from $11,000 net expense
for the quarter ended September 30, 1997. Interest income net of interest
expense as a percentage of revenue increased to 1.5% for the quarter ended
 
                                       10
<PAGE>
September 30, 1998 from 0.0% for the quarter ended September 30, 1997. This
increase was primarily attributable to the investment of the net proceeds from
the Company's initial public offering in February 1998.
 
    INCOME TAXES.  The provision for income taxes of 48.4% in the quarter ended
September 30, 1998 decreased from the 55.5% reported for the quarter ended
September 30, 1997 due to a reduction in certain nondeductible
compensation-related expenses partly offset by the existence of nondeductible
foreign losses in the current period.
 
RESULTS OF OPERATIONS FOR THE NINE MONTHS ENDED SEPTEMBER 30, 1998 AND 1997
 
    NET REVENUE.  The Company's net revenue increased to $94.6 million, or
42.7%, for the nine months ended September 30, 1998 from $66.3 million for the
nine months ended September 30, 1997. This increase was primarily attributable
to an increase in revenue from the Company's implementation, operations
effectiveness, and integration services.
 
    COST OF SERVICES.  Cost of services increased to $51.8 million, or 33.5%,
for the nine months ended September 30, 1998 from $38.8 million for the nine
months ended September 30, 1997. The increase was primarily attributable to an
increase in the number of consultants. Cost of services as a percentage of
revenue decreased to 54.8% for the nine months ended September 30, 1998 from
58.6% for the nine months ended September 30, 1997. This decrease was primarily
attributable to increased realization of standard fees and a higher proportion
of billable associates to total associates during the nine months ended
September 30, 1998.
 
    GENERAL AND ADMINISTRATIVE EXPENSES.  General and administrative expenses
increased to $32.8 million, or 43.9%, for the nine months ended September 30,
1998 from $22.8 million for the nine months ended September 30, 1997. General
and administrative expenses as a percentage of revenue increased to 34.7% for
the nine months ended September 30, 1998 from 34.4% for the nine months ended
September 30, 1997. This increase was primarily attributable to an increase in
the Company's hiring, including hiring for its expansion into Europe.
 
    COMPENSATION EXPENSES RELATED TO STOCK ISSUANCES.  Compensation expenses
related to stock issuances decreased to zero for the nine months ended September
30, 1998 from $1.9 million for the nine months ended September 30, 1997. This
decrease was attributable to the discontinuance of certain compensatory stock
and option issuances.
 
    INTEREST INCOME, NET.  Interest income, net of interest expense, increased
to $1.3 million for the nine months ended September 30, 1998 from $59,000 net
expense for the nine months ended September 30, 1997. Interest income net of
interest expense as a percentage of revenue increased to 1.4% for the nine
months ended September 30, 1998 from (0.1%) for the nine months ended September
30, 1997. This increase was primarily attributable to the investment of net
proceeds resulting from the Company's initial public offering in February 1998.
 
    INCOME TAXES.  Income taxes as a percentage of income before income taxes
decreased to 48.0% for the nine months ended September 30, 1998 from 55.4% for
the nine months ended September 30, 1997 due to a reduction in certain
nondeductible compensation related expenses partly offset by the existence of
nondeductible foreign losses in the current period.
 
    FCG's net revenue and operating results may fluctuate significantly because
of a number of factors, many of which are outside FCG's control. These factors
may include: losing key personnel and other employees, losing one or more
significant clients, consummating an acquisition, costs of integrating acquired
operations, timing and collection of payments and new client engagements, delays
in securing and
 
                                       11
<PAGE>
completing client engagements, fluctuations in market demand for FCG's services,
consultant hiring and utilization, variability in the number of billable days,
availability of foreign net operating losses and other credits against FCG's
earnings, increased competition and pricing pressures, changes in business
strategy, pricing and billing policies of FCG and its competitors, and
international currency fluctuations. A substantial portion of FCG's expenses,
particularly personnel and related costs, depreciation, office rent and
occupancy costs, are relatively fixed. One or more of the foregoing factors may
cause FCG's operating expenses to be disproportionately high during any given
period. In addition, FCG bills certain of its services on a fixed-price basis,
and any assignment delays or expenditures of time beyond that projected for the
assignment could result in write-offs of client billings. Significant write-offs
could materially adversely effect FCG's business, financial condition and
results of operations. Based on the preceding factors, FCG may experience a
shortfall in revenue or earnings or otherwise fail to meet public market
expectations, which could materially adversely effect FCG's business, financial
condition and the market price of the FCG common stock.
 
LIQUIDITY AND CAPITAL RESOURCES
 
    During the nine months ended September 30, 1998, the Company generated cash
flow from operations of $7.5 million. During the nine months ended September 30,
1998, the Company used cash flow of approximately $3.4 million to purchase
property and equipment, including computer and related equipment and office
furniture. Depreciation and amortization expense for the nine months ended
September 30, 1998 was approximately $2.3 million. During the nine months ended
September 30, 1998, the Company generated cash flow of $45.0 million from
financing activities. At September 30, 1998, the Company had working capital of
$31.6 million and long term investments of $25.8 million. At December 31, 1997,
the Company had working capital of $9.3 million. The primary reason for the
increase was the completion of the Company's initial public offering in February
1998.
 
    The Company has a revolving line of credit which allows the Company to
borrow up to $6.0 million at an interest rate of the prevailing prime rate. The
revolving line of credit expires on December 31, 1998. There was no outstanding
balance under the line of credit at September 30, 1998. The Company has two term
loan facilities ("Term Loan A" and "Term Loan B"). Term Loan A is a $305,000
facility under which approximately $241,000 was outstanding as of September 30,
1998. Term Loan A expires on July 1, 2003. Term Loan B is a $4.0 million
facility under which approximately $174,000 was outstanding as of September 30,
1998. Term Loan B expires on December 4, 2001. Term Loan A and Term Loan B bear
interest at a rate per annum equal to the prevailing prime rate plus 0.5%. All
borrowings under the Company's credit facilities are secured by the Company's
accounts receivable and other rights to payment, general intangibles and
equipment. The line of credit agreement provides that the Company must satisfy
certain covenants and restrictions.
 
YEAR 2000 COMPLIANCE
 
    Many existing computer programs and systems, including those used by FCG's
clients, use only two digits to identify the year in the date field. These
programs may be unable to process date/time information between the twentieth
and twenty-first centuries. This inability could cause the disruption or failure
of such computer systems (the "Y2K Problem"). Solving the Y2K Problem will
require a large amount of time and resources. FCG's clients may have to
reallocate a significant portion of their budgets away from FCG's services to
address this problem. Such reallocations would have a material adverse effect on
FCG's business, financial condition and results of operations. Additionally,
FCG's current time and billing systems for its internal use are not Y2K
compliant. FCG has purchased an upgrade to these systems that will render them
Y2K compliant and expects to complete deployment of this upgrade in the first
quarter of 1999. There can be no assurance that such deployment will begin as
planned or, if begun, will be completed in a timely and cost-effective manner.
 
                                       12
<PAGE>
                          PART II.  OTHER INFORMATION
 
ITEM 1. LEGAL PROCEEDINGS.
 
    None.
 
ITEM 2. CHANGES IN SECURITIES.
 
    Under the Company's 1994 Restricted Stock Plan, (the "1994 Plan") the
Company has entered into Restricted Stock Agreements ("RSAs") with each of its
vice presidents. The 1994 Plan and RSAs provide that each person, upon becoming
a vice president of the Company, must purchase and hold a minimum number of
shares of common stock of the Company ("Common Stock").
 
    On July 20, August 20, and September 28, 1998, the Company issued an
aggregate of 73,870 shares (the "Shares") of Common Stock to certain of its vice
presidents (the "Purchasing Vice Presidents") pursuant to the 1994 Plan. The
Purchasing Vice Presidents paid an aggregate of $1,369,011 in consideration of
the Shares. The Shares were issued in reliance on Section 4(2) and Rule 701
promulgated under the Securities Act of 1933, as amended.
 
ITEM 3. DEFAULTS UPON SENIOR SECURITIES.
 
    None.
 
ITEM 4. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS.
 
    None.
 
ITEM 5. OTHER INFORMATION.
 
    None.
 
ITEM 6. EXHIBITS AND REPORTS ON FORM 8-K.
 
    (A) EXHIBITS
 
<TABLE>
<CAPTION>
  ITEM                                                   DESCRIPTION
---------  --------------------------------------------------------------------------------------------------------
<C>        <S>
 3(i)(1)   Certificate of Incorporation of the Company.
3(ii)(1)   Bylaws of the Company.
 4.1(1)    Specimen Common Stock Certificate.
 11.1(2)   Statement of computation of per share earnings.
  27.1     Financial Data Schedule.
</TABLE>
 
------------------------
 
(1) Filed with the Company's Registration Statement on Form S-1, File No.
    333-41121, declared effective on February 12, 1998, incorporated herein by
    reference.
 
(2) See Note 5 to Consolidated Financial Statements, "Net Income Per Share."
 
    (B) REPORTS ON FORM 8-K
 
    On September 10, 1998, the Company filed a report on Form 8-K relating to
the Company's proposed merger with Integrated Systems Consulting Group, Inc.
 
    On September 23, 1998, the Company filed a report on Form 8-K relating to
the Company's proposed merger with Integrated Systems Consulting Group, Inc.
 
                                       13
<PAGE>
                                   SIGNATURES
 
    Pursuant to the requirements of the Securities and Exchange Act of 1934, the
registrant has duly caused this report to be signed in its behalf by the
undersigned thereunto duly authorized.
 
<TABLE>
<S>                                             <C>
                                                FIRST CONSULTING GROUP, INC.
 
Date: November 12, 1998                         /s/ LUTHER J. NUSSBAUM
                                                -------------------------------------------
                                                Luther J. Nussbaum
                                                Chief Executive Officer
 
Date: November 12, 1998                         /s/ THOMAS A. REEP
                                                -------------------------------------------
                                                Thomas A. Reep
                                                Chief Financial Officer and Vice President,
                                                Finance (Principal Financial and Accounting
                                                Officer)
</TABLE>
 
                                       14
<PAGE>
                                 EXHIBIT INDEX
 
<TABLE>
<CAPTION>
 NO. OF
 EXHIBIT                                                 DESCRIPTION
---------  --------------------------------------------------------------------------------------------------------
<C>        <S>
 3(i)(1)   Certificate of Incorporation of the Company.
3(ii)(1)   Bylaws of the Company.
 4.1(1)    Specimen Common Stock Certificate.
 11.1(2)   Statement of computation of per share earnings.
  27.1     Financial Data Schedule.
</TABLE>
 
------------------------
 
(1) Filed with the Company's Registration Statement on Form S-1, File No.
    333-41121, declared effective on February 12, 1998, incorporated herein by
    reference.
 
(2) See Note 5 to Consolidated Financial Statements, "Net Income Per Share."