Her television roles included The Forsyte Saga (1967) I, Claudius (1976), and George Lucas's Young Indiana Jones (1992–1993).

In 1977 she joined the acting company of the Stratford Festival in Canada, where she played Mrs Alving in Ibsen's Ghosts, Queen Margaret in Richard III and the Countess of Roussillon in All's Well That Ends Well.

[4] In a feature of Stratford's 1977 season, New York Times writer Richard Eder noted "One of the main excitements was the discovery of Margaret Tyzack [...] her work here has been a revelation".

She came to notice as Winifred, Soames's sister, in the well received BBC adaptation of Galsworthy's The Forsyte Saga in 1967, a series shown internationally.

[11] She portrayed the character of Gladys King in Dennis Potter's The Bone Grinder (1968), a metaphor for the decline of the British Empire and rise of American power in the post-war world.

She also played Clotilde Bradbury-Scott in the BBC adaptation of the Agatha Christie story Nemesis in 1987 in Miss Marple.

[15] On 13 April 2011, it was announced that for personal reasons she had departed EastEnders and that her role had been recast to Heather Chasen as a result of the nature of the large storyline needing to continue.