At 16, Baxter screen-tested for the role of Mrs. DeWinter in "Rebecca". Director Alfred Hitchcock deemed Baxter too young for the role, but she soon secured a seven-year contract with 20th Century Fox. In 1940, she was loaned to MGM for her first film "20 Mule Team", in which she was billed fourth after Wallace Beery, Leo Carrillo, and Marjorie Rambeau. She worked with John Barrymore in her next film "The Great Profile" (1940) and appeared as the ingénue in the Jack Benny vehicle "Charley's Aunt" (1941). She received star billing in "Swamp Water" (1941) and "The Pied Piper" (1942), which was nominated for the Academy Award for Best Picture.