Garson attended the University of California, Berkeley, where she earned a B.A. specializing in Classical History in 1964. She was active in the Free Speech Movement, as the editor of The Free Speech Movement Newsletter. In the early 1970s, she moved to Manhattan, publishing short, humorous essays and theater reviews primarily for The Village Voice as well as plays.
Garson's most famous work, MacBird!, a 1966 counterculture drama/political parody of Macbeth. It was originally intended for an anti-war teach-in at Berkeley. The first edition had sold over 200,000 copies when the play opened in New York in a production starring Stacy Keach, William Devane, Cleavon Little, and Rue McClanahan. While these then-unknown actors went on to become fixtures in American theater, movies and television, the author "disappeared from public view at the height of fame". The play has since seen over 300 productions worldwide and sold over half a million copies". MacBird! is remembered as an attack on then-U.S. President Lyndon Johnson. In fact, it presented Johnson's predecessor, John Kennedy, and his would-be successor Robert Kennedy as equally unacceptable but more dangerously alluring. Garson wanted her fellow 1960s activists to step away from the Democratic Party and create their own institutions, including a third party. Critical reaction was mixed and the play "has had advocates and detractors of equal stature."
Garson's next full-length play, Going Co-op (1972), was a comedy about residents of an Upper West Side apartment house going co-op and a floundering left wing political collective that comes home to help organize the tenants who cannot afford to change from renters to owners. It was written with Fred Gardner, who is credited with founding the first of the Vietnam-era GI Coffee Houses.
Garson's musical children's play The Dinosaur Door, set on a class trip to the Natural History Museum, was performed at the Theater for the New City in 1976. It featured a cast of children including seven-year-old Mark Vincent, now known as the action hero Vin Diesel. It was awarded an Obie for playwriting in 1977.
A full-length play, The Department (1983), written for and performed by the organizing group Women Office Workers (WOW), is set in a bank's back office that is about to be automated. The Department, though a light farce, sets out many of the problems that Garson expands on in her 1989 book The Electronic Sweatshop.
