Routinely described as one of her generation's finest actors, Ms. Thompson did not gain stardom until she was in her 40s, and was fixed in the public imagination as somebody's mother—often wise and noble, sometimes selfish and terrible, but always a figure of age and experience. Her breakout performance was in the original, 1970 staging of Paul Zindel's The Effect of Gamma Rays on Man-in-the-Moon Marigolds, in which she played the self-involved, unpleasant, slatternly mother of two very different children. "Sada Thompson does ample justice to both the ugliness and the remounts of humanity in Beatrice's character," wrote critic John Simon, "and manages the comic undertones as securely as the overtones of metaphysical horror."
She earned a Drama Desk Award and an Obie for her work in the Zindel play. Two years later, she won her Tony Award, as well as another Drama Desk Award, for Twigs, a group of four short plays by George Furth. In it she portrayed three different daughters as well as their mother. Other notable early performances include the horrendous Mommy in Edward Albee's early, cuttingly absurdist one-act American Dream, and the winsome, hopeful, doomed Winnie in Samuel Beckett's Happy Days.
But her matronly image derived for the most part from "Family," the 1970s landmark drama in which she starred alongside James Broderick, Meredith Baxter Birney and Kristy McNichol. She was Emmy-nominated four times for her performance as Kate Lawrence, the calm, dignified head of family who's everyday troubles were handled with an unusual amount of delicacy and seriousness. The show was applauded for dealing with issues—marital strife, homosexuality, divorce, infidelity—that were either taboo or ignored by other shows. Ms. Thompson won an Emmy for "Family" in 1978. She was also nominated for Emmys for her Mary Todd Lincoln in "Lincoln" (1976); Jack Lemmon's wife in "The Entertainer" (1976); "Our Town" (1978); "Cheers," in which she played Rhea Perlman's mother (1991); and "Indictment: The McMartin Trial" (1995).
She was born Sada Carolyn Thompson on Sept. 27, 1929, in Des Moines, IA, and raised in New Jersey. She became hooked on acting after her parents took her to Cole Porter's Red, Hot and Blue. After earning a degree from the Carnegie Institute of Technology, she began to work in regional theatre and Off-Broadway in classical and modern plays such as The Misanthrope (Drama Desk Award, along with The River Line), Ivanov, The Seagull, Pygmalion, Our Town and Blithe Spirit. Her Off-Broadway debut was in the original production of Dylan Thomas' ode to small-town Welsh life, Under Milkwood. She played Emilia in a 1964 production of Othello in Central Park, opposite the Othello of James Earl Jones.
She married Donald Stewart in 1949. He survives her, as well as a daughter.