He became known in the early 1970s with his political comic drama Don's Party, and other well-known plays include The Club, Travelling North, and Emerald City.

Williamson's work as a playwright focuses on themes of politics, loyalty and family in contemporary urban Australia, particularly in two of its major cities, Melbourne and Sydney.

[1] Major stage works include The Club, The Department, Travelling North, The Perfectionist, Emerald City, Money and Friends and Brilliant Lies.

Reviewing the book for The Sydney Morning Herald, Peter Craven wrote "He comes across as a likeable, flawed fellow with no more blindness than people of lesser talent".

[citation needed] In August 2006 Cate Molloy, former Australian Labor Party member of the Queensland Parliament for Noosa, announced that Williamson would be her campaign manager as she sought to recontest her seat as an Independent.