Grayson trained as an opera singer starting at age 12. She was under contract to MGM by the early 1940s. Most of her work was in musicals. She was the lead in movies such as "Thousands Cheer" (1943), "Anchors Aweigh" (1945) with Frank Sinatra and Gene Kelly,"Show Boat" (1951) and "Kiss Me Kate" (1953) (both with Howard Keel).