Monday's surprise announcement comes the same day O'Brien starts a two-month, 30-city live tour in Eugene, Ore., amid persistent reports that he was likely to claim Fox as his new late-night home.
O'Brien left NBC in January after hosting "The Tonight Show" for just eight months. His predecessor in that slot, Jay Leno, then reclaimed the hour. As part of his parting deal, O'Brien is barred from appearing on TV until September.
