OSU/Umatilla County Extension Service OSU/Umatilla County Extension Service Search | Advanced Search | New Members | Coupons and Discounts | All Categories Other >> Agriculture & Farm Markets OSU/Umatilla County Extension Service PO Box 100Pendleton, OR 97801 | View on Google Maps Accounts Payable OSU (541) 278-5403 Visit Site Connect With Us Hours: Mon-Fri 8 a.m-Noon; 1 p.m.-5 p.m. Member Since: 1996