A versatile writer and editor, he wrote book reviews for The New York Times, did analytical reporting from the United Nations and produced whimsical pieces about two denizens of Montreal's Point St. Charles – Mrs. Harrigan and Mrs. Mulcahy – discussing the vital issues of the day, which were published in the Montreal Star and later issued in book form.
O'Hearn was in wide demand as a speaker, particularly because of his insight and understanding of what he considered one of the most important stories in North America — the rise of French nationalism in Quebec.
He served four terms as director of The Canadian Press, was an officer of the Corporation des Quotidiens du Québec (Quebec Dailies, Inc.), and a member of the Montreal arts council.
With his first wife, the former Mary McGrath, O'Hearn had a son, Walter Jr., a lawyer in New York, and three daughters, Eileen, Catherine and Julia.
With his second wife, the former Dorothy Fletcher, he had two sons, Michael (deceased) and Peter, known as Yeshe Gyamtso, a respected translator of Tibetan texts.