She is best known for her role as Vi Munson in Coming Home (1978) for which she was nominated for an Academy Award for Best Supporting Actress.
She also originated the role of Jenny Anderson in the Broadway musical Shenandoah, for which she was nominated for a Drama Desk Award in 1975.
Also in 1980 she co-starred in the Emmy Award winning television movie The Oldest Living Graduate starring Henry Fonda and Cloris Leachman.
In 1982 she starred opposite Sondra Locke in the Jackie Cooper directed Emmy Award winning television film Rosie: The Rosemary Clooney Story.
In 1984, Penelope appeared in the Golden Globe award-winning television movie The Burning Bed starring Farrah Fawcett.
Her last few films include Cold Justice (1989), Miss Missouri (1990), Normal Life (1996), Henry: Portrait of a Serial Killer, Part II (1996) and Night of the Lawyers (1997).