In 1945, he briefly understudied for John Raitt in the Broadway hit "Carousel" before being assigned to "Oklahoma!" both written by Richard Rodgers and Oscar Hammerstein II. While performing in "Oklahoma," Keel accomplished a feat that has never been duplicated on Broadway; he once performed the leads in both shows on the same day. In 1947, "Oklahoma!" became the first American postwar musical to travel to London, England, and Keel joined the production. On April 30, 1947, at the Drury Lane Theatre, the capacity audience (which included the future Queen Elizabeth II) demanded fourteen encores.