Knowlden had a small part as Florence Udney in the 1936 epic historical drama film "Anthony Adverse", again with Fredric March in a leading role, and Olivia de Havilland as his leading lady. It was nominated for Best Picture at the 9th Academy Awards the following year. She was cast in "Rainbow on the River" (1936), starring Bobby Breen, one of the few children's films that Knowlden ever appeared in. A reviewer from Detroit Free Press lauded her performance as Lucille Layton, calling her "a fine little actress". In the 1938 historical drama film "Marie Antoinette", she portrayed princess Marie Thérèse of France, daughter of the title character, which was played by Norma Shearer. She also played Laurie Martin, James Cagney's character's love interest, as a child in "Angels with Dirty Faces" the same year.