Edward Philip O'Neill, Jr. was born on April 12, 1946, in Youngstown, Ohio, to Ed, Sr., a steelworker and truck driver, and Ruth Ann Quinlan, a social worker, both of Irish-American descent.
Growing up, O'Neill was a gifted athlete and attended Ohio University on a football scholarship. He later transferred to Youngstown State University, where he played as a defensive lineman.
In 1969, he was drafted by the Pittsburgh Steelers but was cut during training camp. After being cut, O'Neill returned to Youngstown State University to join the new theater department.
After graduating, he became a social studies teacher at his alma mater, Ursuline High School, before committing fully to acting. He was a member of the company at the American Repertory Theater in Cambridge, Massachusetts.
O'Neill's early career included numerous supporting parts in movies and television. He was cast as New York City detective Popeye Doyle in the 1986 television movie "Popeye Doyle," which was based on the classic police drama "The French Connection."
The television movie and O'Neill's performance received good reviews, but it was not picked up as a series. A year later, he was cast as Al Bundy in the sitcom "Married with Children," which debuted on the then-new Fox Network in April 1987.
The show ran for 10 years, until June 1997, and made O'Neill a star. During the production of "Married with Children" and after its cancellation, O'Neill appeared in movies, guested on television shows, and made television commercials.
The second iconic fictional policeman role that O'Neill took over was Sgt. Joe Friday in the 2003 remake of Jack Webb's classic crime series "Dragnet." The show appeared on ABC and was canceled during its second season.
Since 2009, O'Neill has played Jay Pritchett on the ABC sitcom "Modern Family," for which he was nominated for an Emmy Award in 2011. He has been married to actress Catherine Rusoff since 1986 and has two daughters, Claire and Sophia.