O'Loughlin appeared in an episode of the 1961 television series "The Asphalt Jungle". In 1966 he portrayed truck driver Carl Munger in a season 2 episode 7 show of "The F.B.I." He appeared in three episodes of "Hawaii Five-O". The first was aired January 29, 1969 in the episode "The Box". O'Loughlin played the tough but sympathetic central figure of a group of prison inmates who take Hawaii Five-O chief Steve McGarrett (Jack Lord) hostage. The second was called "Six Kilos" on March 12, 1969 (playing the same character as in "The Box"), and the third was called "A Time to Die" on September 16, 1970. He also appeared on "Cannon" on February 22, 1972, in the episode "Flight of the Hawks". He also appeared on episode 16 of the TV show "The Green Hornet." In Season 2 Episode 22 of "", he played a killer for hire.