<PAGE>
 
                                                                  EXHIBIT 99(A)

                      OBJECTIVE SYSTEMS INTEGRATORS, INC.

                       1995 EMPLOYEE STOCK PURCHASE PLAN
                     (AS AMENDED THROUGH OCTOBER 17, 1998)


The following is the 1995 Employee Stock Purchase Plan of Objective Systems
Integrators, Inc.


1.   PURPOSE.  The purpose of the Plan is to provide employees of Objective
     -------                                                               
     Systems Integrators, Inc. and its Designated Subsidiaries with an
     opportunity to purchase OSI's Common Stock through accumulated payroll
     deductions. It is intended that this Plan qualify as an "Employee Stock
     Purchase Plan" under Section 423 of the Internal Revenue Code of 1986, as
     amended. The provisions of the Plan, accordingly, will be construed to
     extend and limit participation in a manner consistent with the requirements
     of that Section of the Code.

2.   DEFINITIONS.
     ----------- 

     (a)  BOARD.  The Board of Directors of Objective Systems Integrators, Inc.
          -----                                                                

     (b)  CODE.  The Internal Revenue Code of 1986, as amended.
          ----                                                 

     (c)  COMMON STOCK.  The Common Stock of Objective Systems Integrators,
          ------------ 
          Inc.

     (d)  OSI.  Objective Systems Integrators, Inc. and any of its Designated
          ---                                                                
          Subsidiaries.

     (e)  COMPENSATION.  All of a Participant's W-2 compensation.
          ------------                                           

     (f)  DESIGNATED SUBSIDIARIES.  Each Subsidiary which has been designated by
          -----------------------                                               
          the Board, from time to time and in its sole discretion, as eligible
          to participate in the Plan.

     (g)  EMPLOYEE.  An individual who is employed by OSI for tax purposes and
          --------                                                            
          whose customary employment with OSI is at least 20 hours per week and
          at least five months in any calendar year. For purposes of the Plan,
          the employment relationship will be treated as continuing intact while
          an individual is on sick leave or other leave of absence approved by
          OSI. If the period of leave exceeds 90 days and the individual's right
          to reemployment is not guaranteed either by statute or by contract,
          the employment relationship will be deemed to have ended on the 91st
          day of the leave.

     (h)  ENROLLMENT DATE.  The first day of each Offering Period.
          ---------------                                         

     (i)  EXERCISE DATE.  The last day of each Purchase Period.
          -------------                                        

     (j)  FAIR MARKET VALUE.  As of any date, the value of Common Stock
          -----------------                                            
          determined as follows:

          (1)  If the Common Stock is listed on an established stock exchange or
               a national market system, Fair Market Value will be the closing
               sale price (or the mean of the closing bid and asked prices, if
               no sales were reported), as quoted on the exchange (or the
               exchange with the greatest volume of trading in Common Stock) or
               system on the date of the determination, as reported in The Wall
               Street Journal or such other source as the Board deems reliable,
               or;

          (2)  If the Common Stock is quoted on the Nasdaq National Market of
               the National Association of Securities Dealers, Inc. Automated
               Quotation System (but not on the Nasdaq National Market thereof)
               or is regularly quoted by a recognized securities dealer but
               selling prices are not reported, Fair Market Value will be the
               mean of the closing bid and asked prices for the Common Stock on
               the date of the determination, as reported in The Wall Street
               Journal or such other source as the Board deems reliable, or;

          (3)  In the absence of an established market for the Common Stock,
               Fair Market Value will be determined in good faith by the Board.

                                           OSI 1995 Employee Stock Purchase Plan
                                                                October 17, 1998
                                                                          Page 1
<PAGE>
 
          (4)  For purposes of the Enrollment Date for the first Offering
               Period, Fair Market Value will be the price to the public as set
               forth in the final Prospectus included in the Registration
               Statement (Form S-1) filed with the Securities and Exchange
               Commission for the initial public offering of OSI's Common Stock.

     (k)  OFFERING PERIOD.  The period of approximately 6 months during which an
          ---------------                                                       
          option granted under the Plan may be exercised, beginning on the first
          Trading Day on or after May 1 and November 1 of each year and ending
          on the last Trading Day of the period six months later. The first
          Offering Period will begin on the effective date of OSI's initial
          public offering of Common Stock registered with the Securities and
          Exchange Commission and will end on the last Trading Day on or before
          October 31, 1997. The duration and timing of Offering Periods may be
          changed under Section 4.

     (l)  PLAN.  This Employee Stock Purchase Plan.
          ----                                     

     (m)  PURCHASE PRICE.  An amount equal to 85% of the Fair Market Value of a
          --------------                                                       
          share of Common Stock on the Enrollment Date or on the Exercise Date,
          whichever is lower.

     (n)  PURCHASE PERIOD.  The approximately six-month period beginning after
          ---------------                                                     
          one Exercise Date and ending with the next Exercise Date, except that
          the first Purchase Period of an Offering Period will begin on the
          Enrollment Date and end with the next Exercise Date.

     (o)  RESERVES.  The number of shares of Common Stock covered by each option
          --------                                                              
          under the Plan which have not yet been exercised plus the number of
          shares of Common Stock which have been authorized for issuance under
          the Plan but not yet placed under option.

     (p)  SUBSIDIARY.  A corporation, domestic or foreign, of which not less
          ----------
          than 50% of the voting shares are held by OSI or a Subsidiary, whether
          or not that corporation now exists or is later organized or acquired
          by OSI or a Subsidiary.

     (q)  TRADING DAY.  A day on which national stock exchanges and the Nasdaq
          -----------                                                         
          System are open for trading.

3.   ELIGIBILITY.
     ----------- 

     (a)  Any Employee who is employed by OSI on a given Enrollment Date is
          eligible to participate in the Plan.

     (b)  Any provisions of the Plan to the contrary notwithstanding, no
          Employee will be granted an option under the Plan (1) if, immediately
          after the grant, the Employee (or any other person whose stock would
          be attributed to the Employee under Section 424(d) of the Code) would
          own capital stock of OSI and/or hold outstanding options to purchase
          such stock possessing five percent or more of the total combined
          voting power or value of all classes of OSI's capital stock or that of
          any Subsidiary, or (2) which permits the Employee's rights to purchase
          stock under all employee stock purchase plans of OSI and its
          subsidiaries to accrue at a rate which exceeds $25,000 worth of stock
          (determined at the fair market value of the shares at the time the
          option is granted) for each calendar year in which the option is
          outstanding at any time.

4.   OFFERING PERIODS.  The Plan will be implemented by consecutive Offering
     ----------------                                                       
     Periods, with a new Offering Period beginning on the first Trading Day on
     or after May 1 and November 1 each year, or on such other date as the Board
     determines, and continuing thereafter until terminated in accordance with
     Section 19. The first Offering Period will begin on the Effective Date of
     OSI's initial public offering of Common Stock registered with the
     Securities and Exchange Commission. The Board may change the duration of
     Offering Periods (including their commencement dates) for future offerings
     without shareholder approval if the change is

                                           OSI 1995 Employee Stock Purchase Plan
                                                                October 17, 1998
                                                                          Page 2
<PAGE>
 
     announced at least five days before the scheduled beginning of the first
     Offering Period to be affected.

5.   PARTICIPATION.
     ------------- 

     (a)  An eligible Employee may become a Participant in the Plan (a
          "Participant") by completing a subscription agreement in the form of
          Exhibit A to this Plan and filing it with OSI's payroll office before
          the applicable Enrollment Date.

     (b)  Payroll deductions for Participants will begin on the first payroll
          after the Enrollment Date and will end on the last payroll in the
          Offering Period to which the authorization is applicable, unless
          sooner terminated by a Participant under Section 10.

6.   PAYROLL DEDUCTIONS.
     ------------------ 

     (a)  At the time a Participant files a subscription agreement, the
          Participant will elect to have payroll deductions made on each pay day
          during the Offering Period. Deductions may not exceed 15% of the
          Compensation which the Participant receives on each pay day. The
          aggregate of all payroll deductions during an Offering Period may not
          exceed 15% of the Participant's Compensation during the Offering
          Period.

     (b)  Payroll deductions will be credited to a Participant's account under
          the Plan and will be withheld in whole percentages only. Participants
          may not make any additional payments into their accounts.

     (c)  Participants may stop participating in the Plan as provided in Section
          10. They may also increase or decrease their rate of payroll
          deductions once during a Purchase Period by filing a new subscription
          agreement with OSI authorizing the change. The Board may, in its
          discretion, limit the number of rate changes during any Purchase
          Period. Rate changes will be effective with the first full payroll
          period that begins at least five business days after OSI receives the
          new subscription agreement unless OSI elects to process a given change
          more quickly. Subscription agreements will remain in effect for
          successive Offering Periods unless terminated under Section 10.

     (d)  Notwithstanding the foregoing, to the extent necessary to comply with
          Section 423(b)(8) of the Code and Section 3(b) of this Plan, a
          Participant's payroll deductions may be decreased to 0% during a
          Purchase Period ("Current Purchase Period") if the sum of all payroll
          deductions previously used to purchase stock under the Plan in an
          earlier Purchase Period ending during the same calendar year, plus all
          payroll deductions accumulated for the Current Purchase Period, equals
          $21,250. Thereafter, payroll deductions will recommence at the
          beginning of the first Purchase Period which ends in the next calendar
          year and at the rate in the Participant's subscription agreement,
          unless terminated by the Participant under Section 10.

     (e)  At the time the option is exercised, in whole or in part, or at the
          time some or all of the Common Stock issued under the Plan is disposed
          of, Participants must make adequate provision for OSI's federal,
          state, or other tax withholding obligations, if any, which arise on
          the exercise of the option or the disposition of the Common Stock. OSI
          may, but will not be obligated to, withhold from a Participant's
          compensation at any time the amount necessary for it to meet
          applicable withholding obligations, including withholding required to
          make available to OSI any tax deductions or benefits attributable to
          the Participant's sale or early disposition of Common Stock.

7.   GRANT OF OPTION.  On the Enrollment Date of each Offering Period, eligible
     ---------------                                                  
     Employees participating in the Offering Period will be granted an option to
     purchase on each Exercise Date during the Offering Period (and at

                                           OSI 1995 Employee Stock Purchase Plan
                                                                October 17, 1998
                                                                          Page 3
<PAGE>
 
     the applicable Purchase Price) up to a whole number of shares of Common
     Stock determined by dividing the payroll deductions accumulated by the
     Employee before the Exercise Date and retained in the Employee's account as
     of the Exercise Date, by the applicable Purchase Price. The preceding
     sentence notwithstanding, (a) no Participant can purchase during a Purchase
     Period more than a number of shares determined by dividing $12,500 by the
     Fair Market Value of a share of Common Stock on the Enrollment Date, and
     (b) all purchases will be subject to the limitations in Sections 3(b) and
     12. Exercise of the option will occur as provided in Section 8 (unless the
     Participant has withdrawn under Section 10) and will expire on the last day
     of the Offering Period.

8.   EXERCISE OF OPTION.  Unless a Participant withdraws from the Plan under
     ------------------                                                     
     Section 10, the option to purchase shares will be exercised automatically
     on the Exercise Date. The maximum number of whole shares subject to option
     will be purchased for each Participant at the applicable Purchase Price
     with the accumulated payroll deductions in the Participant's account. No
     fractional shares will be purchased. Any payroll deductions accumulated in
     the Participant's account which are insufficient to purchase a whole share
     will be retained for the subsequent Purchase Period or Offering Period,
     subject to earlier withdrawal under Section 10. Any other money left over
     in a Participant's account after the Exercise Date will be returned. During
     a Participant's lifetime, only the Participant can exercise the option to
     purchase shares under the Plan.

9.   DELIVERY.  As promptly as practicable after each Exercise Date on which a
     --------                                                               
     purchase of shares occurs, OSI will arrange for the delivery to each
     Participant, as appropriate, of a certificate representing the shares
     purchased on exercise of the option.

10.  WITHDRAWAL AND TERMINATION OF EMPLOYMENT.
     ---------------------------------------- 

     (a)  At any time, Participants may withdraw all but not less than all of
          the payroll deductions credited to their account and not yet used to
          exercise an option under the Plan. Withdrawal will be effected by
          giving OSI notice in the form of Exhibit B. All of the payroll
          deductions credited to a Participant's account will be paid to the
          Participant promptly after OSI receives notice of withdrawal, the
          Participant's option for the Offering Period will automatically be
          terminated and no further payroll deductions for the purchase of
          shares will be made for the Offering Period. If a Participant
          withdraws from an Offering Period, payroll deductions will not resume
          at the beginning of the next Offering Period unless the Participant
          has delivered a new subscription agreement to OSI.

     (b)  On ceasing to be an Employee for any reason, Participants are deemed
          to have withdrawn from the Plan. The payroll deductions credited to
          the Participant's account during the Offering Period but not yet used
          to exercise the option will be returned to the Participant (or, in the
          case of the Participant's death, to the person entitled to them under
          Section 14) and the Participant's option will automatically be
          terminated. The preceding sentences notwithstanding, Participants who
          receive payment in lieu of termination notice will be treated as
          continuing to be Employees for their customary number of hours per
          week of employment during the period in which they are subject to the
          payment in lieu of notice.

11.  INTEREST.  No interest will accrue on the payroll deductions of 
     --------                                                       
     Participants.

12.  COMMON STOCK.
     ------------ 

     (a)  The maximum number of shares of Common Stock that will be made
          available for sale under the Plan is 1,487,500, subject to adjustment
          on changes in OSI's capitalization as provided in Section 18. If, on
          any Exercise Date, the number of shares for which options are to be
          exercised exceeds the number of shares then available under the Plan,
          OSI will make a pro rata allocation of the shares remaining available
          for purchase in as uniform a manner as practicable and as it
          determines to be equitable.

     (b)  Participants will have no interest or voting right in shares covered
          by their options until the options have been exercised.

     (c)  Shares to be delivered to Participants under the Plan will be
          registered in the name of each Participant or in the name of each
          Participant and his or her spouse.


                                           OSI 1995 Employee Stock Purchase Plan
                                                                October 17, 1998
                                                                          Page 4
<PAGE>
 
13.  ADMINISTRATION.  The Plan will be administered by the Board or a committee
     --------------                                                  
     of the Board duly appointed by the Board (either, as applicable, being
     referred to as the "Board"). The Board will have full and exclusive
     discretionary authority to construe, interpret and apply the terms of the
     Plan, to determine eligibility and to adjudicate all disputed claims filed
     under the Plan. Every finding, decision or determination made by the Board
     will, to the fullest extent permitted by law, be final and binding on all
     parties.

14.  DESIGNATION OF BENEFICIARIES.
     ---------------------------- 

     (a)  A Participant may file a written designation of a beneficiary who is
          to receive the shares and cash, if any, from the Participant's account
          if the Participant dies after an Exercise Date but before the shares
          and cash have been delivered to the Participant. A Participant may
          also file a written designation of a beneficiary who is to receive any
          cash from the Participant's account if the Participant dies before the
          option is exercised. If a Participant is married and the designated
          beneficiary is not his or her spouse, spousal consent will be required
          for these designations to be effective.

     (b)  Participants may change their designated beneficiary at any time by
          notice to OSI. If a Participant dies and there is no validly
          designated beneficiary who is living at that time, OSI will deliver
          the shares and/or cash to the executor or administrator of the
          Participant's estate. If no executor or administrator has been
          appointed to OSI's knowledge, then OSI, in its discretion, may deliver
          the shares and/or cash to the spouse or to any one or more of the
          Participant's dependents or relatives. If no spouse, dependent or
          relative is known to OSI, then OSI, in its discretion, may deliver the
          shares and/or cash to such other person as OSI designates.

15.  TRANSFER.  Participants may not assign, transfer, pledge or otherwise
     --------                                                             
     disposed of in any way (other than by will, the laws of descent and
     distribution or as provided in Section 14) either payroll deductions
     credited to their account or any rights with regard to the exercise of
     options or the receipt of shares under the Plan. Any attempt at assignment,
     transfer, pledge or other disposition will be without effect, except that
     OSI may treat the attempt as an election to withdraw from an Offering
     Period under Section 10.

16.  USE OF FUNDS.  All payroll deductions received or held by OSI under the
     ------------                                                           
     Plan may be used by OSI for any corporate purpose. OSI will not be
     obligated to segregate payroll deductions.

17.  REPORTS.  Individual accounts will be maintained for each Participant.
     -------                                                                
     Statements of account will be given to each Participant at least once per
     year. These statements will set forth the amounts of payroll deductions,
     the Purchase Price, the number of shares purchased and the remaining cash
     balance, if any.

18.  ADJUSTMENTS ON CHANGES IN CAPITALIZATION, DISSOLUTION, LIQUIDATION, MERGER
     --------------------------------------------------------------------------
     OR ASSET SALE.
     -------------

     (a)  Subject to any required action by OSI's stockholders, the Reserves and
          the price per share of Common Stock covered by unexercised options
          under the Plan will be proportionately adjusted for any change in the
          number of issued shares of Common Stock as a result of a stock split,
          reverse stock split, stock dividend, combination or reclassification
          of the Common Stock, or any other change in the number of shares of
          Common Stock effected without OSI receiving consideration. For
          purposes of the Plan, however, the conversion of any convertible
          securities of OSI will not be deemed to have been "effected without
          receipt of consideration". This adjustment will be made by the Board,
          whose determination will be final and binding. Except as provided in
          the Plan, no issuance by OSI of any class of stock or securities
          convertible into shares of any class of stock, will affect (and no
          adjustment by reason of such an issuance will be made with respect to)
          the number or price of Common Stock under option.

     (b)  Unless otherwise provided by the Board, if dissolution or liquidation
          of OSI is proposed, the Offering Periods will end immediately before
          the proposed action is consummated.

     (c)  If a sale of all or substantially all of OSI's assets or a merger of
          OSI with or into another corporation is proposed, each option under
          the Plan will be assumed (or an equivalent option will be substituted
          by) the successor corporation, its parent or one of its subsidiaries,
          unless the Board determines, in its sole


                                           OSI 1995 Employee Stock Purchase Plan
                                                                October 17, 1998
                                                                          Page 5
<PAGE>
 
          discretion and in lieu of the assumption or substitution, to shorten
          the Offering Periods then in progress by setting a new Exercise Date
          (the "New Exercise Date"). If the Board sets a new Exercise Date, it
          will notify each Participant in writing, at least 10 business days
          before the New Exercise Date. This notice will set forth that the
          Exercise Date has been changed to the New Exercise Date and that
          options will be exercised automatically on the New Exercise Date,
          unless before that date the Participant has withdrawn from the
          Offering Period as provided in Section 10. For purposes of this
          Subsection, an option will be deemed to have been assumed if, after
          the sale or merger, the option confers the right to purchase, for each
          share of Common Stock subject to the option immediately before the
          transaction, the same consideration (whether stock, cash or other
          securities or property) received in the transaction by holders of
          Common Stock for each share of their Common Stock. In making this
          determination, if the holders of Common Stock were offered a choice of
          consideration, the type of consideration chosen by the holders of a
          majority of the outstanding shares of Common Stock will apply.
          Notwithstanding the preceding sentences, if the consideration received
          in the transaction was not solely common stock of the successor
          corporation or its parent (as defined in Section 424(e) of the Code),
          the Board may, with the consent of the successor corporation, provide
          for the consideration to be received on exercise of the option to be
          solely common stock of the successor corporation or its parent equal
          in fair market value to the per share consideration received by
          holders of Common Stock in the transaction.

19.  AMENDMENT OR TERMINATION.
     ------------------------ 

     (a)  The Board may, at any time and for any reason, amend or terminate the
          Plan. Except as provided in Section 18, (1) no amendment may make any
          change in an option previously granted which adversely affects the
          rights of a Participant, and (b) no termination can affect options
          previously granted, except that the Board may terminate an Offering
          Period on any Exercise Date if it determines that termination of the
          Offering Period is in the best interests of OSI and its stockholders.
          To the extent necessary to comply with any applicable law, rule or
          regulation, OSI will obtain all required stockholder approvals for
          amendments to the Plan.

     (b)  Without stockholder consent and without regard to whether any
          Participant rights have been "adversely affected," the Board may
          change the Offering Periods, limit the frequency and/or number of
          changes in the amount withheld during an Offering Period, establish
          the exchange ratio applicable to amounts withheld in a currency other
          than U.S. dollars, permit payroll withholding in excess of the amount
          designated by a Participant in order to adjust for delays or mistakes
          in OSI's processing of properly completed withholding elections,
          establish reasonable waiting and adjustment periods and/or accounting
          and crediting procedures to ensure that amounts applied toward the
          purchase of Common Stock for each Participant properly correspond with
          amounts withheld from the Participant's Compensation, and establish
          such other limitations or procedures as the Board determines, in its
          sole discretion, to be advisable and consistent with the Plan.

20.  NOTICES.  All notices or other communications by a Participant to OSI in
     -------                                                              
     connection with the Plan will be in writing and will be deemed to have been
     duly given when received in the form specified by OSI and at the location,
     or by the person, designated by OSI to receive it.

21.  CONDITIONS ON ISSUANCE OF SHARES.
     -------------------------------- 

     (a)  Shares will not be issued with respect to an option unless the
          exercise of the option and the issuance and delivery of the shares
          complies with all applicable provisions of law, domestic or foreign,
          and has been approved in respect of that compliance by counsel to OSI.
          This includes, without limitation, the Securities Act of 1933, as
          amended, the Exchange Act, the rules and regulations promulgated under
          both, and the requirements of any stock exchange on which the Common
          Stock may then be listed.

     (b)  If a representation is required in the opinion of OSI's counsel, then
          OSI may require the person


                                           OSI 1995 Employee Stock Purchase Plan
                                                                October 17, 1998
                                                                          Page 6
<PAGE>
 
          exercising an option to represent and warrant, as a condition of
          exercise and at the time of exercise, that the Common Stock is being
          purchased only for investment and without any present intention to
          sell or distribute it.

22.  TERM OF PLAN.  The Plan will become effective on the earlier of its
     ------------                                                       
     adoption by the Board or its approval by the stockholders of OSI. It will
     continue in effect for a term of 10 years unless sooner terminated under
     Section 19.

23.  AUTOMATIC TRANSFER TO LOWER PRICE OFFERING PERIOD.  To the extent permitted
     -------------------------------------------------                          
     by applicable law, if the Fair Market Value of the Common Stock on an
     Exercise Date in an Offering Period is lower than the Fair Market Value of
     the Common Stock on the Enrollment Date of the Offering Period, then all
     Participants in the Offering Period will be automatically withdrawn from
     that Offering Period immediately after the exercise of their options on the
     Exercise Date and automatically re-enrolled in the immediately following
     Offering Period as of its first day.


                                           OSI 1995 Employee Stock Purchase Plan
                                                                October 17, 1998
                                                                          Page 7
<PAGE>
 
                                   EXHIBIT A
                                   ---------
                                        
                      OBJECTIVE SYSTEMS INTEGRATORS, INC.

                       1995 EMPLOYEE STOCK PURCHASE PLAN
                                        
                            SUBSCRIPTION AGREEMENT
                                        

_____ Original Application                          Enrollment Date: ___________
_____ Change in Payroll Deduction Rate
_____ Change of Beneficiary(ies)


1.   ________ elects to participate in the Objective Systems Integrators, Inc.
     1995 Employee Stock Purchase Plan (the "Plan") and subscribes to purchase
     shares of OSI's Common Stock in accordance with this Subscription Agreement
     and the Plan.

2.   I hereby authorize payroll deductions from each paycheck in the amount of
     _____ of my Compensation on each payday (1-15%) during the Offering Period
     in accordance with the Plan. (Please note that no fractional percentages
     are permitted.)

3.   I understand that these payroll deductions will be accumulated for the
     purchase of OSI Common Stock at the applicable Purchase Price determined in
     accordance with the Plan. I understand that if I do not withdraw from an
     Offering Period, any accumulated payroll deductions will be used to
     automatically exercise my option.

4.   I have received a copy of the complete Plan. I understand that my
     participation in the Plan is in all respects subject to the terms of the
     Plan. I understand that my ability to exercise the option under this
     Subscription Agreement is subject to obtaining shareholder approval of the
     Plan.

5.   Shares purchased for me under the Plan should be issued in the name(s) of
     (Employee or Employee and spouse only): _____________________________.

6.   I understand that if I dispose of any shares received by me under the Plan
     within 2 years after the Enrollment Date (the first day of the Offering
     Period during which I purchased the shares) or one year after the Exercise
     Date, I will be treated for federal income tax purposes as having received
     ordinary income at the time of disposition in an amount equal to the excess
     of the fair market value of the shares at the time such shares were
     purchased over the price which I paid for them. I AGREE TO NOTIFY OSI IN
                                                     ------------------------
     WRITING WITHIN 30 DAYS AFTER THE DATE OF ANY DISPOSITION OF MY SHARES AND I
     ---------------------------------------------------------------------------
     WILL MAKE ADEQUATE PROVISION FOR FEDERAL, STATE OR OTHER TAX WITHHOLDING
     ------------------------------------------------------------------------
     OBLIGATIONS, IF ANY, WHICH ARISE ON THE DISPOSITION OF THE COMMON STOCK.
     -----------------------------------------------------------------------  
     OSI may, but will not be obligated to, withhold from my compensation the
     amount necessary to meet any applicable withholding obligation including
     any withholding necessary to make available to OSI any tax deductions or
     benefits attributable to my sale or early disposition of Common Stock. If I
     dispose of shares at any time after the expiration of the 2-year and 1-year
     holding periods, I understand that I will be treated for federal income tax
     purposes as having received income only at the time of disposition, and
     this such income will be taxed as ordinary income only to the extent of an
     amount equal to the lesser of (a) the excess of the fair market value of
     the shares at the time of disposition over my purchase price, or (b) 15% of
     the fair market value of the shares on the first day of the Offering
     Period. The remainder of the gain, if any, recognized on disposition will
     be taxed as capital gain.

7.   I agree to be bound by the terms of the Plan. The effectiveness of this
     Subscription Agreement depends on my eligibility to participate in the
     Plan.

8.   If I die, I designate the following as my beneficiary(ies) to receive all
     payments and shares due me under the 


                                           OSI 1995 Employee Stock Purchase Plan
                                                                October 17, 1998
                                                                          Page 8
<PAGE>
 
     Plan:



     NAME: (Please print) _____________________________________________

                          (First)        (Middle)        (Last)


                          _____________________________________
                          Relationship

                          _____________________________________________

                          _____________________________________________

                          _____________________________________________
                          Address



Employee's Social
Security Number:          _____________________________________________



Employee's Address:       _____________________________________________

                          _____________________________________________
 
                          _____________________________________________


I UNDERSTAND THAT THIS SUBSCRIPTION AGREEMENT WILL REMAIN IN EFFECT THROUGHOUT
SUCCESSIVE OFFERING PERIODS UNLESS I TERMINATE IT.



Dated: _________________________        ________________________________________
                                        Signature of Employee


                                        ________________________________________
                                        Spouse's Signature (If beneficiary other
                                        than spouse)


                                           OSI 1995 Employee Stock Purchase Plan
                                                                October 17, 1998
                                                                          Page 9
<PAGE>
 
                                   EXHIBIT B
                                   ---------
                                        
                      OBJECTIVE SYSTEMS INTEGRATORS, INC.

                       1995 EMPLOYEE STOCK PURCHASE PLAN
                                        
                             NOTICE OF WITHDRAWAL
                                        

The undersigned Participant in the Offering Period of the Objective Systems
Integrators, Inc. 1995 Employee Stock Purchase Plan which began on ____________,
19__ (the "Enrollment Date") gives notice to OSI of his or her election to
withdraw from the Offering Period. The Participant directs OSI to pay to the
Participant as promptly as practicable all the payroll deductions credited to
the Participant's account with respect to that Offering Period. The Participant
understands and agrees that the option for this Offering Period will be
automatically terminated. The Participant also understands and agrees that no
further payroll deductions will be made for the purchase of shares in the
current Offering Period. The Participant will be eligible to participate in
succeeding Offering Periods only by delivering a new Subscription Agreement to
OSI.


                                        Name and Address of Participant:


                                        ________________________________________
 
                                        ________________________________________
 
                                        ________________________________________
 

                                        Signature:


                                        ________________________________________

 
                                        Date: __________________________________



                                           OSI 1995 Employee Stock Purchase Plan
                                                                October 17, 1998
                                                                         Page 10