O'Brien graduated with an honours Bachelor of Arts in history from the University of Western Ontario in 1971, and earned his Master of Education from UWO in 1981.
He has frequently chastised Prime Minister Paul Martin for not allowing a free vote among his Cabinet on Bill C-38, which is the act to legalize same-sex marriage in Canada.
On June 6, 2005, O'Brien left the Liberal Party to sit as an independent, citing his opposition to same-sex marriage, and his discomfort with the revelations coming out of the Gomery Commission on the sponsorship scandal.
In the fall of 2005, O'Brien announced that he and a former Conservative MP were founding an advocacy group to try to reverse the legalization of same-sex marriage.
Since leaving Parliament, he has remained active in conservative Canadian politics, appearing at the REAL Women of Canada convention in 2010.