Ms. Tyzack was a stage animal primarily, and was well-rewarded in her native country for her devotion. She won two Laurence Olivier Awards, one for playing Martha in a 1981 revival of Edward Albee’s Who’s Afraid of Virginia Woolf? and another in 2009 for playing Mrs. St. Maugham in Enid Bagnold’s 1950s comedy The Chalk Garden. She additionally won an Evening Standard Theatre Award for the latter.

To American theatregoers, she was best known for holding her own against a flowery, scenery-chewing Maggie Smith in the 1991 Broadway production of Peter Shaffer’s comedy Lettice and Lovage. She played a travel agency worker of infinite patience, waiting on the eccentricities of Smith's batty tour guide. Many critics commented on the connection on stage between the two actresses, who had created the parts in the London premiere of the play. The actress was almost denied the job, since, initially, Actors' Equity had refused to let the British performer travel with the show, arguing that she wasn't a big enough star. When Smith said she would not perform without Ms. Tyzack, the actors union relented.

"In the much less thankful, rather underwritten role of Lotte, Miss Tyzack is every bit as dizzying as Miss Smith," wrote critic John Simon. "Just as the play's will-o'-the-wispy faintest and the earthbound sourpuss—the Yea and the Nay—need each other, neither actress could shine so starrily if the other's light were less diamantine. You'll have no difficulty admiring Miss Smith's razzle-dazzle, but consider no less Miss Tyzack's concentrate of deflation, her horrifiedly acerb reactions, her eventual blushing conversion." Ms. Tyzack won a Tony Award for her performance.

Ms. Tyzack's outlook was as sensible as the character she played in the Shaffer play. She was modest and enjoyed anonymity. While long a leading player, she was never quite a leading lady, usually gravitating toward character roles—a situation that reportedly pleased her just fine. "As far as I'm concerned, acting is a job," she once said. "Oh, it's a lovely, lovely job—but it's a job, and one I drifted into."

Her only other Broadway appearance was in 1983, when she was nominated for a Tony Award for her Countess of Rousillon in All’s Well That Ends Well, a role she played several times during her career. She also appeared Off-Broadway, in 1985's Tom and Viv at the Public Theater, and was nominated for a Drama Desk Award. She had perviously essayed the role at the Royal Court Theatre. Margaret Tyzack was born Sept. 9, 1931, in Essex, England, and grew up in West Ham. A graduate of RADA, she joined the Royal Shakespeare Company in 1962, making her debut there in The Lower Depths. She would go on to play Volumnia, Portia and Tamora in Titus Andronicus. "I was in more plays in a single year than some actors will perform in their entire careers," she said of her early career. "It was my education. We weren't spoiled or indulged. It was very hard work, and the paying ­customer came first."

In 1977, she did a season at the Stratford Festival in Canada, in such plays as Ghosts and Richard III. On the West End, she acted in Vivat! Vivat Regina (1971), An Inspector Calls (1983) and Morning's at Seven.

Her film appearances were not as prominent as her stage turns, but were in quality projects. She appeared in the Stanley Kubrick classics "2001: A Space Odyssey" and "A Clockwork Orange," Stephen Frear's "Prick Up Your Ears," and Woody Allen's "Match Point." On television, she was Winifred Dartie in the 1967 BBC version of "The Forsyte Saga"—a 1967 mini-series that brought her her first taste of fame (it aired in the U.S. in 1969)—Antonia, the title character's mother, in "I, Claudius," Queen Anne in "The First Churchills," Bette in "Cousin Bette," and and Miss Seymour, teenage Indy's tutor in "The Young Indiana Jones Chronicles."

Later roles included Samuel Adamson's Southwark Fair at the National Theatre, Morris Panych's Auntie and Me on the West End, and, in 2009, Phedre opposite Helen Mirren at the National.

In 1958, she married Alan Stephenson, with whom she had one son, Matthew.