Usually plays senior law enforcement or military officers
Graduated from Auburn University.
O'Neill grew up in Montgomery, Alabama. In 2011, after many decades living outside of the state, he bought a house in the Cahaba Heights neighborhood of Birmingham, Alabama, so that he could spend more time with his ailing father. Even after his father's death, he still splits his time between Birmingham and Marina Del Ray, California.
He has three daughters: Ella, Annie, and Molly O'Neill.