In 1937, as "Nan Barto", Walker appeared on the NBC radio programs "Coast to Coast on a Bus" and "Our Barn." She made her Broadway debut in 1941 in "Best Foot Forward." The role provided Walker with her film debut, when she signed a contract with Metro-Goldwyn-Mayer to appear in the 1943 film version, starring Lucille Ball. She also appeared with Mickey Rooney and Judy Garland in the second film version of "Girl Crazy" (1943). Her next film, "Broadway Rhythm", in which she had a featured musical number backed by Tommy Dorsey and His Orchestra, "Milkman, Keep Those Bottles Quiet", ended Walker's contract with MGM.