Harris made an auspicious film debut, recreating her stage role of Frankie in Fred Zinnemann's "The Member of the Wedding" (1952). While she was too old to be believable as a twelve year old, she nevertheless offered an impressive portrayal, aided by co-stars Brandon De Wilde and especially Ethel Waters, and earned a Best Actress Oscar nomination. Harris never fully emerged as a film star, but over the years has given a number of fine, nuanced performances. She was again able to repeat a stage role in "I Am a Camera" (1955), a somewhat stagy rendering. (The material was handled far more superbly by Bob Fosse with 1972's "Cabaret"). That same year, Harris excelled as a young woman torn between two brothers (James Dean, Richard Davalos) in Elia Kazan's "East of Eden". She was superb as an eccentric spinster in Robert Wise's chilling "The Haunting" (1963) and offered fine support as a drug addict in "Harper" and an odd landlady in "You're a Big Boy Now" (both 1966) and as Brian Keith's unstable wife in John Huston's "Reflections in a Golden Eye" (1967). In 1975, she earned critical praise in the fact-based drama "The Hiding Place" as a Dutch woman whose family works to save Jews during WWII and later are imprisoned in a concentration camp. Harris was fine as the mother of a mentally unbalanced writer in "The Bell Jar" (1979) and limned her stage version of Charlotte Bronte in "Bronte" (1983). Other notable credits include Sigourney Weaver's mentor in "Gorillas in the Mist" (1988), Steve Martin's estranged mother in "Housesitter" (1992), Timothy Hutton's eccentric colleague in "The Dark Half" (1993) and Dennis Hopper's dying mother in "Carried Away" (1996).

Since the late 40s, Harris has been gracing the small screen in specials, guest appearances and as a series regular. Like many of her associates, she first appeared on TV in "Actors Studio" (ABC, 1948). Over the years she headlined numerous prestige projects, including numerous episodes of "Hallmark Hall of Fame", including Emmy-winning turns in "Little Moon of Alban" (NBC, 1958) and "Victoria Regina" (NBC, 1961). Additionally, she appeared in "The Lark" (NBC, 1957), "Pygmalion" (NBC, 1963), and "Anastasia" (NBC, 1967). Harris made guest appearances on series ranging from "Goodyear Television Playhouse" to "Tarzan" to "The Love Boat". Telefilms include "How Awful About Allan" (ABC, 1970), "Home for the Holidays" (ABC, 1972) and "The Christmas Wife" (HBO, 1988), opposite Jason Robards. Harris was a regular on three series. In 1973, she co-starred in "Thicker Than Water" (ABC), a short-lived sitcom in which she and Richard Long were siblings forced to run the family pickle factory. She fared only slightly better as Glenn Ford's supportive wife in the Depression-era drama "The Family Holvak" (NBC 1975). Harris won her biggest audience when she joined the CBS primetime soap "Knots Landing" in 1981. For six years, she played Lillimae Clements, the mother of heroine Valene (Joan Van Ark) and the shifty Joshua (Alec Baldwin). In recent years, in addition to co-starring in TV-movies (like Sally Field's directorial debut "The Christmas Tree" ABC, 1996), Harris has been lending her dulcet, throaty tones as a voice actor on projects like Ken Burns' acclaimed "The Civil War" (PBS, 1990), Burns' "Baseball" (PBS, 1994), "Mary Lincoln's Insanity File" (The Discovery Channel, 1996) and "The West" (PBS, 1996) as well as several recordings and radio broadcasts.