SCHEDULE 14A INFORMATION
 
                  Proxy Statement Pursuant to Section 14(a) of
                      the Securities Exchange Act of 1934
 
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         Section 240.14a-12
 
                                QUICKTURN DESIGN SYSTEMS, INC.
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                (Name of Registrant as Specified In Its Charter)
 
                                 MENTOR GRAPHICS CORPORATION
- --------------------------------------------------------------------------------
    (Name of Person(s) Filing Proxy Statement, if other than the Registrant)
 
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          MENTOR GRAPHICS NOTIFIES QUICKTURN STOCKHOLDERS OF CHANGE IN
                     LOCATION OF OCTOBER 29 SPECIAL MEETING
 
    WILSONVILLE, OR, OCTOBER 19, 1998 -- Mentor Graphics Corporation (Nasdaq:
MENT) today said that is has mailed to stockholders of Quickturn Design Systems,
Inc. (Nasdaq: QKTN) an Amended and Supplemental Notice changing the location of
the October 29, 1998 Special Meeting from Dover, Delaware to The Corporation
Trust Company, 1209 Orange Street, Wilmington, Delaware.
 
    The principal purpose of the Special Meeting is to vote on replacing the
Quickturn Board of Directors with a slate of independent directors nominated by
Mentor Graphics. If the nominees are elected, Mentor Graphics expects that,
subject to their fiduciary duties to all Quickturn stockholders, the nominees
will take the steps necessary to facilitate the stockholders' ability to accept
Mentor Graphics' $12.125 per share all-cash offer. A trial on Mentor Graphics'
challenge to Quickturn's anti-takeover actions and Mentor Graphics' scheduling
of the Special Meeting is commencing today in Delaware state court.
 
    The text of Mentor Graphics' letter to Quickturn stockholders follows:
 
                              [MENTOR LETTERHEAD]
 
                                IMPORTANT NOTICE
 
                                                                October 16, 1998
 
Dear Quickturn Stockholder:
 
    THE LOCATION OF THE SPECIAL MEETING OF STOCKHOLDERS OF QUICKTURN DESIGN
SYSTEMS, INC., CALLED BY MENTOR GRAPHICS CORPORATION FOR OCTOBER 29, 1998 AT 3
P.M. NEW YORK CITY TIME, HAS BEEN CHANGED TO THE CORPORATION TRUST COMPANY, 1209
ORANGE STREET, WILMINGTON (COUNTY OF NEW CASTLE), DELAWARE 19801. As you know,
the Special Meeting was previously scheduled to take place at the offices of The
Corporation Trust Company in Dover, Delaware as provided in the Notice of
Special Meeting sent to you on September 11, 1998. The foregoing constitutes the
Amended and Supplemental Notice of Special Meeting to holders of record of
Quickturn common stock as of the close of business on September 10, 1998, the
record date for the October 29 Special Meeting.
 
    Mentor Graphics had set the Special Meeting in Dover, Delaware based on a
provision in Quickturn's bylaws. Quickturn filed a motion in Delaware state
court today stating that Quickturn's certificate of incorporation, which
provides for Wilmington, Delaware as the location of the Special Meeting, should
control over the bylaw provision. By waiting for over a month to even mention
this, the motion is another example of Quickturn's ongoing effort to delay the
vote at the Special Meeting and frustrate the will of stockholders who want to
accept our $12.125 per share, fully financed, all-cash offer. Mentor Graphics
will provide round-trip transportation to the Wilmington, Delaware location for
any stockholder who appears at the Dover, Delaware location.
 
                                   -BULLETIN-
 
    It is important for you to know that, on October 14, 1998, Institutional
Shareholder Services Inc. (ISS), one of the nation's leading institutional
shareholder advisory firms, has recommended to its clients that they vote in
favor of Mentor Graphics' director nominees and related proposals at the Special
Meeting. In it report, ISS states: "At best, ISS views the [Quickturn] board's
action as an overzealous execution of its perceived fiduciary duty to
shareholders. At worst, we must give weight to the self-preservation effects
that the takeover defenses produce on behalf of the board and management at the
potential expense of shareholders. Fiduciary duty does not include eliminating
or obstructing the rights of shareholders to determine to accept any offer for
their ownership in the company."
 
    The ISS report concludes: "The board's duty would have been more properly
executed by placing its argument squarely in opposition to the offer of [Mentor]
and allowing shareholders to exercise right to vote democratically and
expeditiously on the matter."

                        VOTE YOUR GOLD PROXY CARD TODAY!
 
    If you have any questions or need assistance in voting Mentor Graphics' GOLD
proxy card, please call MacKenzie Partners, Inc., which can be reached at
800-322-2885 Toll-Free or at 212-929-5500 (Collect).
 
                                          Sincerely,
 
                                          Walden C. Rhines
                                          President and Chief Executive Officer
 
    The Dealer Manager for Mentor Graphics' tender offer is Salomon Smith
Barney.
 
                                               
Contacts:  Anne M. Wagner                            Roy Winnick/Todd Fogarty
           Vice President, Marketing                 Kekst and Company
           503/685-1462                              212/521-4800


 
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