Harper is best known for her portrayal of the wise-cracking yet vulnerable Rhoda Morgenstern on two CBS television sitcoms of the 1970s: The Mary Tyler Moore Show and its spin-off Rhoda, in which she played the title role. Harper won four Emmy awards and a Golden Globe for her work as Rhoda Morgenstern on both series.
She also played family matriarch Valerie Hogan on the 1980s sitcom Valerie's Family. (It was renamed The Hogan Family in 1987 after Harper left the series and was replaced by Sandy Duncan).
Harper has worked almost exclusively in television, and has also had roles in made-for-TV-movies and guest spots on a number of series, including Sex and the City.
Harper was born in Suffern, New York.