In 2008, he appeared as a guest star on several episodes of "Brothers & Sisters". His feature film credits include "The Anniversary Party", "21 Grams", "Garden State", "Derailed", "Michael Clayton", "A Mighty Heart", "Half Nelson", "Milk", "Edge of Darkness", "Charlie Wilson's War" and "Changeling". In 2009, O'Hare portrayed Phillip Steele (an amalgam character based on Quentin Crisp's friends Phillip Ward and Tom Steele) in a television biopic on Crisp entitled "An Englishman in New York". The same year he played therapist Dr. David Worth in the series "Bored to Death" (episode 1.3).