A graduate of Northwestern University's famed drama program, Rae took off for New York once she had her degree and made her New York stage debut in 1952 in "Three Wishes for Jamie" on Broadway. She scored a greater Broadway triumph playing Mammy Yokum in the musical "Li'l Abner" (1956) and later performed with the New York Shakespeare Festival in numerous plays, including playing the Nurse in "Romeo and Juliet" (1968). Rae was making TV appearances simultaneous to her Broadway runs in the 50s, starting with a guest shot on the "U.S. Steel Hour" (ABC, 1954). She also appeared on several episodes of "The Phil Silvers Show" in the mid-50s, but did not have a recurring role on a series until "Car 54, Where Are You?" (NBC, 1961-63), in which she was Sylvia Schnausser, wife to Al Lewis. It was more than a decade before Rae had another regular series berth. Having migrated to Los Angeles, she was cast in the short-lived "The Hot L Baltimore" (ABC, 1975), produced by Norman Lear's company, and then on the ill-fated "Rich Little Show" (NBC, 1976). In 1978, Lear tapped her again to play Mrs. Garrett on "Diff'rent Strokes". In 1979, her character was shifted to the spin-off "The Fact of Life", with Rae as a housemother at a girl's prep school. At the first show sputtered badly, but then after a cast overhaul (several of the young actresses, including Molly Ringwald and Lauren Tom, were dropped) and a change in concept, it became a ratings winner. Mrs. Garrett was moved to being in charge of the cafeteria and all catering for the prep school, with four girls living above the cafeteria and helping out as she helped them to grow up. Later in the series, Mrs. Garrett left the Academy and opened her own "Edna's Edibles" food store.
Tired of the series grind, Rae left the show in the 1986-87 season. (The sitcom went on for several seasons after her departure.) Since then, Rae has been little seen on TV. She had a recurring role as a nurse in the mercy killing cycle on the NBC drama "Sisters" during the 1994-95 season. Rae reunited with her "Facts" co-star Nancy McKeon on an episode of the latter's one-season "Can't Hurry Love" (CBS, 1995).
Rae has also played highly dramatic roles in TV-movies. She was the sister of widowed Maureen Stapleton in "Queen of the Stardust Ballroom" (CBS, 1975) and the mother of a young seamstress who would like her religious parents to give her more leeway in "The Triangle Factory Fire Scandal" (NBC, 1979). Garrett also headlined "The Facts of Life Goes to Paris" (NBC, 1982), a special spawned from the series. Rae has been seen less in feature films. She worked for Woody Allen in "Bananas" (1971) and was "wheelman" Ron Liebman's mother in "The Hot Rock" (1972). Rae provided the voice of Aunt Figg for "Tom & Jerry: The Movie" (1992), and returned to film work with a cameo as a fortune teller for Gregg Araki's "Nowhere" (1997).