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Your Vote Counts! ORION GROUP HOLDINGS, INC. 2021 Annual Meeting Vote by May 19, 2021 10:59 PM CT ORION GROUP HOLDINGS, INC. 12000 AEROSPACE AVENUE, SUITE 300 HOUSTON, TEXAS 77034 D48525-P54840 You invested in ORION GROUP HOLDINGS, INC. and it’s time to vote! You have the right to vote on proposals being presented at the Annual Meeting. This is an important notice regarding the availability of proxy material for the stockholder meeting to be held on May 20, 2021. Get informed before you vote View the Notice and Proxy Statement and Annual Report online OR you can receive a free paper or email copy of the material(s) by requesting prior to May 6, 2021. If you would like to request a copy of the material(s) for this and/or future stockholder meetings, you may (1) visit www.ProxyVote.com, (2) call 1-800-579-1639 or (3) send an email to sendmaterial@proxyvote.com. If sending an email, please include your control number (indicated below) in the subject line. Unless requested, you will not otherwise receive a paper or email copy. Smartphone users Point your camera here and vote without entering a control number Vote Virtually at the Meeting* May 20, 2021 10:00 a.m., CDT Virtually at: www.virtualshareholdermeeting.com/ORN2021 *Please check the meeting materials for any special requirements for meeting attendance. V1 For complete information and to vote, visit www.ProxyVote.com Control #

Vote at www.ProxyVote.com THIS IS NOT A VOTABLE BALLOT This is an overview of the proposals being presented at the upcoming stockholder meeting. Please follow the instructions on the reverse side to vote these important matters. Board Recommends Voting Items D48526-P54840 Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click “Sign up for E-delivery”. 1. To elect two Class II members to our Board of Directors each to serve a three-year term and until a successor is duly elected and qualified; Nominees: 1a. Michael J. Caliel For 1b. Richard L. Daerr, Jr. For 2. A non-binding advisory proposal to approve the compensation of our named executive officers as disclosed in the proxy statement (the “say-on-pay” vote); For 3. The ratification of the appointment of KPMG LLP as the Company’s independent registered public accounting firm for 2021; and For NOTE: To transact such other business as may properly come before the Annual Meeting or any adjournment thereof.