They join Kings of Leon, Franz Ferdinand and Paul Weller, who were confirmed for the event last month.
Benicassim takes place on July 16, 17, 18 and 19 and tickets are currently on sale. Previous performers at the festival include Radiohead, Depeche Mode, Brian Wilson, Blur, The Strokes and Lou Reed.
"I'm really pleased to have Oasis play this year, especially as it's [Benicassim's] 15th Anniversary," said organiser and Mean Fiddler founder Vince Power. "This year looks to be one of the best years to date."
Benicassim co-founder Jose Morán added: "What better way to celebrate our 15th anniversary than with the confirmation that such a significant band as Oasis will be performing. This will be their third time in Benicassim, after their concerts in 2000 and 2005."