The event takes place from August 12 to August 14 at Cornbury Park, Oxfordshire.
Other performers confirmed for the weekend include Toots and the Maytals, Hayseed Dixie and Guillemots.
The Old Vic Tunnels and The Sundown Orchestra will also present outdoor theatre across the weekend.
Weekend tickets are available now for £99.50 plus booking fee. Day tickets are also on sale for £55.
Marling has already been confirmed for the 2011 End Of The Road and Camp Bestival events.