When does the Orange County Fair occur? May 15, 2019 by Mitchell Mcdonalid·Comments Off on When does the Orange County Fair occur? Share this...FacebookPinterestTwitterLinkedin The Orange County Fair takes place in Costa Mesa. During 2019, it will run from July 12th through August 11th at the OC Fair and Event Center at 88 Fair Drive. This event first occurred in 1890. It draws large crowds every summer. No related posts.