Thursday's was the couple's first appearance in public together since Sharon told her co-hosts on chat show "The Talk" that she was no longer living with her husband.
The festival, named Ozzfest Meets Knotfest, will be headlined by Black Sabbath in what is being billed as their final North American show, and Slipknot.
It will take place on Sep 24 and 25 in San Bernardino.
The Osbournes, who have been married for more than three decades, have become one of Hollywood's most famous couples since starring in a reality television show, "The Osbournes", alongside two of their children, Jack and Kelly, which gave an insight into their family life in Beverly Hills.
Sharon Osbourne, 63, was a regular panellist on US reality TV talent show "America's Got Talent" and played out a battle with colon cancer in public.