Her Broadway debut was in Touchstone (1953), and the following year, she originated the role of Rhoda Penmark, an eight-year-old psychopath and fledgling serial killer, in the original stage version of Maxwell Anderson's The Bad Seed (1954) with Nancy Kelly. She made her motion-picture debut in Two Gals and a Guy (1951) and appeared as Ingeborg in the television series Mama with Peggy Wood from 1953 to 1956. McCormack was a child model at the age of four, and began appearing on television at the age of seven.

The cast of Peck's Bad Girl: From left: Wendell Corey, McCormack, Ray Farrell, Marsha Hunt She was also cast and appeared as Adriana La Cerva's mother in The Sopranos. She also appeared in the November 11, 1982, season 3 episode 8.'Foiled Again' of Magnum, P.I. Her acting career has continued with both starring and supporting roles in film and television, including Helen Keller in the original Playhouse 90 production of The Miracle Worker, Jeffrey Tambor's wife Anne Brookes on the ABC sitcom The Ropers, and as Pat Nixon in Frost/Nixon (2008). She received critical acclaim for the role on Broadway and was nominated for an Oscar for Best Supporting Actress for her performance in Mervyn LeRoy's film adaptation. She is perhaps best known for her performance as Rhoda Penmark in Maxwell Anderson's 1956 psychological drama The Bad Seed. McCormack began her career as a child actress. Patricia McCormack (born Patricia Ellen Russo in 1945 ) is an American actress with a career in theater, films, and television.

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