Coghlan began his acting career in 1920, appearing with Jack Dempsey in Daredevil Jack. In 1922, he co-starred with Brownie the Dog in a film called Rookies. And in 1923, he played a small role in the Pola Negri film, The Spanish Dancer. He also appeared in early "Our Gang" films, including the 1923 Hal Roach short, "Giants vs. Yanks," in which the gang, after having a baseball game called off, gets stuck in an elegant home which they destroy. In 1924, Coghlan was again cast opposite Jack Dempsey in Winning His Way.
One newspaper story described Coghlan's rise to fame this way: "When the boy was seven years old, his great mop of hair, freckled face, genial grin, and likable personality attracted the attention of several directors who urged his parents to permit him to engage in screen work. Mrs. Coghlan finally consented and one day he was cast for a 'bit' role in Goldwyn's Poverty of Riches, in which he played the son of Leatrice Joy."
