His character on The Secret Storm was Kip Rysdale, who was the husband of the heroine of that show, Amy Ames, played by actress Jada Rowland. In 1976, the two actors were reunited when Rowland joined the cast of The Doctors as the second Carolee Aldrich, the wife of O'Brien's character.
One of his later roles was as Dr. Alan Glaser on Another World (1986-87). The role started out as that of a seemingly good doctor, but in the end, the good doctor was revealed to be the "Sin Stalker," responsible for killing off several supporting characters on the show.
In 1989, O'Brien died from acquired immune deficiency syndrome (AIDS) complications.