In a second successful year with the Royal Shakespeare Company, Helen played Phebe in the RSC production of "As You Like It", and Hero in "Much Ado About Nothing" opposite Janet Suzman and Alan Howard. She also appeared in another feature film - a big screen adaptation by Peter Hall of "A Midsummer Night's Dream", starring as Hermia opposite David Warner, Diana Rigg, Ian Richardson, Ian Holm and Judi Dench. By the end of the year, Mirren would leave England for Australia, shooting a first starring role in a film.

While "Herostratus" and "A Midsummer Night's Dream" didn't exactly raise her movie profile, director Sam Peckinpah auditioned Helen Mirren for a role that would have changed the path of her career. The screenplay, by Peckinpah and David Zelag Goodman, was based upon Gordon M. Williams's 1969 novel, "The Siege of Trencher's Farm". To this day, "Straw Dogs" is noted for its violent concluding sequences and rape scene. Released theatrically in the same year as A Clockwork Orange, The French Connection, and Dirty Harry, the film sparked heated controversy over a perceived increase of violence in films generally. However, Mirren turned down the female lead, she had set her eyes on playing Cressida with the RSC.