1945–1949: Change to Rory Calhoun and partnership with David O. Selznick
Shortly afterward, the Ladds hosted a party attended by David O. Selznick employee Henry Willson, an agent who was known for representing young actors. Willson signed McCown to a contract with Selznick's company Vanguard and his name was soon changed to Rory Calhoun. According to Calhoun, Selznick told him his first name should be "Rory... because you're a Leo, Leos are lions and lions roar." Selznick suggested either Donahue, Calhoun, or Callahan as a surname, and he picked Calhoun. (In another account of the story, Selznick named him "Rory" because he helped put out roaring fire blazes when a firefighter and "Calhoun" because it sounded Irish.)
Calhoun was under contract with Selznick's company Vanguard, being used to do screen tests and make public appearances. His first public appearance in the film capital was as Lana Turner's escort to the premiere of Alfred Hitchcock's Spellbound (1945), a Selznick production. The glamorous blonde and her handsome companion attracted the paparazzi, and photos appeared in newspapers and fan magazines.
In 1945, Calhoun returned to prison after punching a detective.
Calhoun did not appear in a film for a year before being lent to producer Sol Lesser for The Red House (1947) with Edward G. Robinson. He was then loaned to Paramount's Pine-Thomas second feature studio to play the lead in Adventure Island (1947) with fellow Selznick contractee Rhonda Fleming.
Calhoun was announced for a film called Jet Pilot with Fleming, Guy Madison, and other Selznick contract players, but it was not made. Instead, he was third lead in That Hagen Girl (1947) with Ronald Reagan and Shirley Temple.
Sam Newfield, who used Calhoun in Adventure Island, cast him again in Miraculous Journey (1948). For Monogram, Guy Madison and he were in Massacre River (1949). At Fox, Calhoun played a second lead in Sand (1949)
In February 1949, Selznick did a deal with Warner Bros., lending them seven of his stars, including Calhoun; they took over half his pictures for the rest of his contract with Selznick. He played the villain in Return of the Frontiersman (1950) and was hero of Monogram's County Fair (1950).