Last Month, Ticket News says (in Outside Lands Festival adds Lucinda Williams, the Avett Brothers ...)  CT
The previously announced headline acts for the three-day event are Pearl Jam, Dave Matthews Band and Beastie Boys. Also on the bill are Incubus, MIA, Thievery Corporation, Jason Mraz, Ween, The Mars Volta, Black-Eyed Peas, Tom Jones, TV on the Radio, ...

2 Months Ago, San Jose Mercury News says (in San Francisco's Outside Lands lineup announced) In addition to the headliners, this year's lineup includes Incubus, Black Eyed Peas, Jason Mraz, Tom Jones, Ween, Modest Mouse, TV on the Radio, Band of Horses, Silversun Pickups and Q-Tip as well as such up-and-coming acts as Deerhunter and Blind ...
Credit: Beastie Boys HitFix

And Reuters says (in Pearl Jam album, film, tour in the works) Brooklyn Vegan
Along with Dave Matthews Band and the Beastie Boys, the group will headline the festival's second edition, scheduled for August 28-30 at Golden Gate Park. MIA, Modest Mouse, the Mars Volta, Black Eyed Peas, Ween, Thievery Corporation, Incubus and Jason ...

And Los Angeles Times Blogs says (in SF Outside Lands Festival: lineup announced; presale begins April ...) Altsounds.com
 CA
Pearl Jam will be headlining, and other biggies will include the Beastie Boys, Dave Matthews Band, MIA, Thievery Corporation, Incubus and Modest Mouse. There are many more on the list, and more as-yet unannounced acts will likely be made known in the ...

And Rolling Stone says (in Pearl Jam, Beastie Boys, Dave Matthews Band Headlining San ...) MIA, Modest Mouse, the Mars Volta, TV on the Radio, the Dead Weather, Mastodon, Ween, Thievery Corporation, Incubus and Jason Mraz round out the fest’s initial lineup. Pre-sale tickets start Wednesday, April 15th. Get the entire lineup after the jump. ...