O'Malley has also guest-starred in series including My Name Is Earl, Raising Hope, Parenthood and Parks and Recreation, and has appeared in films including 28 Days, Deep Impact, Leatherheads, Eat, Pray, Love, R.I.P.D., Concussion and Sully.
O'Malley is also a published playwright whose plays include Three Years From Thirty and Diverting Devotion. He adapted another play called Searching for Certainty for Peter Askin's film Certainty, which premiered at the Boston Film Festival in 2011. O'Malley is also a writer on Showtime's hit drama Shameless.
O'Malley was the creator and an executive producer of the Starz series Survivor's Remorse, which ran for four seasons between 2014 and 2017.