Forrest began her film career in the 1940s as a chorus dancer in MGM musicals. She made her acting debut in "Not Wanted" (1949), written and produced by Ida Lupino. Its controversial subject of unwed motherhood was a raw and unsentimental view of a condition rarely explored by Hollywood at the time. Forrest starred in two more Lupino projects, "Never Fear" (1949) and "Hard, Fast and Beautiful" (1951), as well as other films noir, including "Mystery Street" (1950), directed by John Sturges, and the star-studded "While the City Sleeps" (1956), directed by Fritz Lang. Her musical background and training as a jazz and ballet dancer brought roles in the transitional musicals that rounded off the golden age of MGM; most notable was "Excuse My Dust" (1951).