Her screen debut came during the silent film era as a thirteen month old baby in 1926, when she appeared alongside her father and her sister Sheila in the western My Old Dutch.

[1] O'Malley went on to appear in several films and television shows during a seven decade career, including Cover Girl, Lady on a Train, Two Tickets to Broadway, Gunsmoke, Maverick, Rawhide, Leave it to Beaver and General Hospital.

[5] In 1943, she played the part of a college girl in the Vincent Sherman directed film Old Acquaintance which starred Bette Davis, Miriam Hopkins and Gig Young.

[11][12] Her character Prudence creates an issue[clarification needed] due to presumably marrying Sandy instead of young Mormon man Jackson.

[15] In 1952, she appeared as Mrs. Norton, a pilot's wife in the Tay Garnett Korean war film One Minute to Zero which starred Robert Mitchum and Ann Blyth.