In high school Preston was interested in music, and appeared in operettas. He appeared in a stock company production of "Julius Caesar" and appeared in a Pasadena Playhouse production of "Idiot's Delight." Preston has said that at a Paramount Pictures attorney liked his work and recruited him to the studio. The "Los Angeles Times" reported that Preston's mother was employed by a company that recorded Bing Crosby phonograph records, and she convinced Crosby's brother Everett, a talent agent, to watch one of his performances at the Pasadena Playhouse. The result was a contract with the Crosby agency and featured roles in "King of Alcatraz ("1938) and "Illegal Traffic".