<PAGE>

                                                                     Exhibit 4.2

    VOID IF NOT RECEIVED BY THE SUBSCRIPTION AGENT BEFORE 5:00 P.M., NEW YORK
                         CITY TIME, ON DECEMBER 19, 2003

   Certificate No.:                            Total Aggregate Value of Shares:

                                                     $
   ---------------                                    ---------------


                                   COSI, INC.
                             SUBSCRIPTION RIGHTS FOR

                     COMMON STOCK, PAR VALUE $0.01 PER SHARE

REGISTERED OWNER:

As the registered owner of this Rights Certificate, you are the owner of the
number of subscription rights (each, a "Right") entitling you to purchase shares
of our common stock having the total aggregate value shown above. Each Right
that you have been issued entitles you to subscribe for and purchase a number of
shares of common stock, par value $0.01 per share ("Common Stock"), with a value
equal to an aggregate of $0.6776, at a purchase price per share equal to the
lesser of (i) $1.50 and (ii) 85% of the weighted average price per share of our
common stock as reported on the Nasdaq National Market for the 15-trading-day
period ending three business days prior to December 19, 2003. You may,
therefore, subscribe to purchase a number of shares of Common Stock having an
aggregate value up to the Total Aggregate Value of Shares shown above. This is
referred to as the "Basic Subscription Privilege." You are not required to
purchase any shares. You may elect to purchase some or all of the shares that
are covered by the Basic Subscription Privilege. If you fully exercise your
Basic Subscription Privilege, and Cosi's Shareholders sub-scribe for less than
an aggregate of $7.5 million pursuant to the Basic Subscription Privilege, you
are eligible to subscribe for and purchase additional shares of Common Stock
that are offered in this Rights Offering but that are not purchased by other
Rights holders. This is referred to as the "Over-subscription Privilege." The
maximum number of shares for which you will be able to subscribe pursuant to
your Over-subscription privilege will equal your pro rata share of the total
amount of shares available for over-subscription. Your pro rata share will be
based upon the total number of shares of our Common Stock and warrants to
purchase shares of our Common Stock you own compared to the total number of
shares of our Common Stock and warrants to purchase shares of our Common Stock
owned by all stockholders who exercised their Over-subscription Privilege and
the "Funding Parties", as described in the accompanying prospectus. If there is
an insufficient number of shares of our common stock remaining unsold after
holders have exercised their Basic Subscription Privilege to satisfy in full all
subscriptions that we receive for additional shares, we will allocate the
available shares among the holders who execute their Over-subscription Privilege
on a pro rata basis according to their respective holdings, up to the amount
such holder has subscribed for through the exercise of such holder's
Over-subscription Privilege. You will be deemed to have exercised the basic
subscription privilege to purchase shares to the full extent of the payment you
tender. If the aggregate subscription price you pay exceeds the amount necessary
to purchase the number of shares you are entitled to purchase pursuant to your
Basic Subscription Privilege, then you will be deemed to have exercised the
Over-subscription Privilege to the full extent of the excess payment tendered.
ONCE YOU HAVE EXERCISED YOUR BASIC SUBSCRIPTION PRIVILEGE OR, IF ELIGIBLE, YOUR
OVER-SUBSCRIPTION PRIVILEGE, YOU MAY NOT REVOKE YOUR EXERCISE. Rights may be
exercised at any time during the subscription period, which commences on
November 25, 2003 and ends at 5:00 p.m., New York City time, on December 19,
2003, unless extended under certain circumstances (as it may be extended, the
"Expiration Date"). After the Expiration Date, unexercised Rights will be null
and void. The Company will not be obligated to honor any purported exercise of
Rights received by American Stock Transfer & Trust Company (the "Subscription
Agent") after the Expiration Date, regardless of when the documents
relating to such exercise were sent, except pursuant to the Guaranteed Delivery
Procedures described in the Instructions as to Use of Rights Certificates which
accompanies this Rights Certificate. The Company may extend the Expiration Date
by giving oral or written notice to the Subscription Agent on or before the
Expiration Date, followed by a public announcement thereof no later than 9:00
a.m., New York City time, on the next business day after the previously
scheduled Expiration Date. The other terms and conditions of these Rights are
set forth in the enclosed Company prospectus (the "Prospectus").

THESE SUBSCRIPTION RIGHTS ARE NON-TRANSFERABLE. You will have no right to
rescind a purchase after the Subscription Agent has received your Rights
Certificate or Notice of Guaranteed Delivery. The Company will not issue
fractional shares of Common Stock upon exercise of Rights. Holders will not
receive cash in lieu of fractional rights or fractional shares.

You have three choices:

1.    You can subscribe for that number of shares of Common Stock, at a price
      per share equal to the subscription price, equal to the Total Aggregate
      Value of Shares, as listed at the top of the page;

      For Example: if you own 1,000 shares of Common Stock, your Basic
      Subscription privilege will entitle you to purchase up to $677.60 worth of
      shares of Common Stock in this Rights Offering. If you choose to fully
      subscribe for your Basic Subscription Privilege, assuming the subscription
      price equals $1.50 per share, you will receive 451 shares, and $1.10 will
      be returned to you (because fractional shares will not be issued).

2.    You may subscribe for a number of shares of Common Stock, at the
      Subscription Price, having a value equal to an amount up to the Total
      Aggregate Value of Shares listed above.

      For Example: if you own 2,000 shares of Common Stock, your Basic
      Subscription privilege will entitle you to purchase up to $1,355.20 worth
      of shares of Common Stock in this Rights Offering. You may choose to
      subscribe for a number of shares of Common Stock having a value equal to
      any amount up to $1,355.20. Assuming you choose to subscribe for a number
      of shares of Common Stock having a value equal to $1,000.00 pursuant to
      your Basic Subscription Privilege, and assuming the Subscription Price
      equals $1.50 per share, you will receive 666 shares, and $0.99 will be
      returned to you (because fractional shares will not be issued).

3.    If you do not want to purchase any shares of Common Stock, you can
      disregard this material.

      To subscribe, full payment of the subscription price is required for the
      aggregate value of Common Stock purchased. You must complete the reverse
      side of this form to subscribe for shares.

      Dated:

--------------------------------------    --------------------------------------
           MARK STICKNEY                                KEVIN ARMSTRONG
CHIEF FINANCIAL OFFICER AND SECRETARY              CHIEF EXECUTIVE OFFICER


COUNTERSIGNED AND REGISTERED:
      AMERICAN STOCK TRANSFER & TRUST COMPANY,
       (NEW YORK, N.Y.)        TRANSFER AGENT
                               AND REGISTRAR

BY:     /s/ illegible
          AUTHORIZED SIGNATURE
<PAGE>
                                                    Certificate No.
                                                                     -----------

                                                        Account No.
                                                                     -----------

                                     Total Aggregate Value of Shares
                                                                     -----------

                     DELIVERY OPTIONS FOR RIGHTS CERTIFICATE

                       By Mail, Hand or Overnight Courier:

                     American Stock Transfer & Trust Company
                                 59 Maiden Lane
                                   Plaza Level
                            New York, New York 10038

Delivery to an address other than the address listed above will not constitute
valid delivery. Delivery by facsimile will not constitute valid delivery.

Please print all information clearly and legibly.
--------------------------------------------------------------------------------
If you wish to subscribe for your full subscription right or a portion thereof:

I subscribe for shares of Common Stock having an aggregate value equal to (1.)
$--------------.00
(Amount enclosed)
--------------------------------------------------------------------------------
If you wish to subscribe for shares pursuant to the Over-subscription Privilege
(subject to limitation, but exercisable only if your Basic Subscription is fully
subscribed for")

I subscribe for shares of Common Stock having an aggregate value equal to (2.)
$--------------.00
(Amount Enclosed)

Total Amount Enclosed (the sum of (1.) and (2.) above) $--------------

I acknowledge that I have received the Prospectus for this Rights offering and I
hereby irrevocably subscribe for a number of shares with an aggregate value
equal to the Total Amount Enclosed indicated above on the terms and conditions
specified in the Prospectus. I hereby agree that if I fail to pay for the shares
of Common Stock for which I have subscribed, the Company may exercise its legal
remedies against me.

Signature(s) of Subscriber(s):              Address for delivery of shares if
                                            other than shown on front:

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

--------------------------------------      ------------------------------------
Please give your telephone number:          (If permanent change of address,
( )-----------------------------------      check here [---].)


Important: The signature(s) must correspond with the name(s) of the registered
holder(s) exactly as it appears on the face of this Rights Certificate without
any alteration or change whatsoever. Persons who sign this Rights Certificate in
a representative or other fiduciary capacity must indicate their capacity when
signing and, unless waived by the Subscription Agent in its sole and absolute
discretion, must present to the Subscription Agent satisfactory evidence of
their authority to so act.

You must have your signature guaranteed if you wish to have your shares
delivered to an address other than that shown on the front. Your signature must
be guaranteed by a member firm of a registered national securities exchange or a
member of NASD Inc., or by a commercial bank or trust company having an office
or correspondent in the United States, or by a bank, stockbroker, savings and
loan association or credit union with membership in an approved signature
guarantee medallion program, pursuant to Rule 17Ad-15 of the Securities Exchange
Act of 1934, as amended Signature Guaranteed:

-------------------------------------         By: -----------------------------
(Name of Bank or Firm)                            (Signature of Officer)

                                METHOD OF PAYMENT

 ALL PAYMENTS MUST BE MADE IN UNITED STATES DOLLARS, PAYABLE TO "AMERICAN STOCK
         TRANSFER & TRUST COMPANY, AS SUBSCRIPTION AGENT - COSI, INC."

(check one)

[ ]   Wire transfer of funds
      Name of transferor institution:------------------------------------------
      Date of transfer:--------------------------------------------------------
      Confirmation number (if available):--------------------------------------

      Wire transfer of immediately available funds directly to the account
      maintained by American Stock Transfer & Trust Company, as Subscription
      Agent - Cosi, Inc., for purposes of accepting subscriptions in this
      Rights offering at JP Morgan Chase Bank, 55 Water Street, New York, New
      York 10005, ABA #021000021, Account # 323-836925.

      Any wire transfer should clearly indicate the identity of the holder who
      is paying the subscription price by the wire transfer.

[ ]   Uncertified check
      Name of maker:------------------------------------------------------------
      Date of check:------------------------------------------------------------
      Check number:-------------------------------------------------------------
      Bank on which check is drawn (must be located in U.S.):-------------------

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

[ ]   Certified check
      Name of maker:------------------------------------------------------------
      Date of check:------------------------------------------------------------
      Check number:-------------------------------------------------------------
      Bank on which check is drawn (must be located in U.S.):-------------------

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

      Bank draft (cashier's check)
      Name of maker:------------------------------------------------------------
      Date of check:------------------------------------------------------------
      Check number:-------------------------------------------------------------
      Bank on which check is drawn (must be located in U.S.):-------------------

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

[ ]   Money order
      Name of maker:------------------------------------------------------------
      Date of check:------------------------------------------------------------
      Check number:-------------------------------------------------------------
      Bank on which check is drawn (must be located in U.S.):-------------------
      --------------------------------------------------------------------------

Please note that funds paid by uncertified personal check may take at least five
business days to clear. Accordingly, Rights holders who wish to pay the
subscription price by means of an uncertified personal check are urged to make
payment sufficiently in advance of the Expiration Date to ensure that such
payment is received and clears by the Expiration Date, and are urged to consider
payment by means of a certified or bank check, money order or wire transfer of
immediately available funds. Crediting of shares acquired in this Rights
offering to any account is subject to collection of checks.

If you do not indicate the aggregate value of Rights being exercised, or do not
enclose or transmit full payment of the total subscription price payment equal
to the amount you indicate above, the Company reserves the right to (1) apply
any payment actually received by the Company toward the purchase of the greatest
number of whole shares that could be acquired by you upon exercise of your
Rights or (2) exercise any and all other rights or remedies to which the Company
may be entitled.

As soon as practicable after the Expiration Date and the valid exercise of
Rights, the Subscription Agent will mail to each exercising Rights holder, to
the address shown on the face of this Rights Certificate unless you provide
instructions to the contrary in the space provided above, certificates
representing shares of Common Stock purchased pursuant to the subscription
Right.