EXHIBIT 99.6 FORM OF INSTRUCTIONS BY BENEFICIAL OWNERS TO BROKERS OR OTHER NOMINEES (accompanying letter from brokers or other nominees to beneficial owners) The undersigned acknowledge(s) receipt of your letter and the enclosed materials referred to therein relating to the offering of shares of Common Stock, par value $0.01 per share (the "Common Stock"), of Grubb & Ellis Company (the "Company"). This will instruct you regarding exercising Rights to purchase the Common Stock distributed with respect to the Company's Common Stock, held by you for the account of the undersigned, pursuant to the terms and subject to the conditions set forth in the Prospectus and the related "Instructions as to Use of Grubb & Ellis Company Subscription Rights Certificates" (the "Instructions"). box 1. [ ] Please do not exercise Rights for shares of the Common Stock. box 2. [ ] Please exercise Rights for shares of the Common Stock as set forth below: NUMBER OF SUBSCRIPTION SHARES PRICE PAYMENT Basic Subscription Right*: _____ X $[INSERT] = $________ (Line 1) ----------------- Oversubscription Right:** _____ X $[INSERT] = $________ (Line 2) ----------------- Total Payment Required = $ ________ (Sum of Lines 1 and 2; must equal total of amounts in boxes 4 and 5 below) * YOU MAY PURCHASE ONE (1) SHARE FOR EACH WHOLE RIGHT YOU HOLD. ** PROVIDED THAT YOU HAVE EXERCISED YOUR ENTIRE BASIC SUBSCRIPTION RIGHT, YOU MAY OVERSUBSCRIBE FOR ADDITIONAL SHARES IN AN AMOUNT UP TO THE GREATER OF (A) 50% OF THE NUMBER OF FULL RIGHTS RECEIVED OR (B) 100 SHARES. THE NUMBER OF ADDITIONAL SHARES THAT YOU MAY RECEIVE PURSUANT TO THIS OVER SUBSCRIPTION PRIVILEGE DEPENDS UPON HOW MANY RIGHTS ARE EXERCISED BY OTHER STOCKHOLDERS, AND IS THEREFORE SUBJECT TO PRORATION. box 3. [ ] Payment in the following amount is enclosed: $_______________ box 4. [ ] Please deduct payment from the following account maintained by you as follows: __________________________ _________________________________ Type of Account Account No. Amount to be deducted: $_________________________________________________ Date:__________________, 2002 _______________________________ Signature (s) (Please sign exactly as your name appears above. Joint owners should each sign personally. Where applicable, please indicate your official position or representative capacity.) Please type or print name(s) below ----------------------------------- 2