Biblical theology
Coffin was ordained a priest in 1971. After serving as assistant curate at St. Matthew's Anglican Church in Ottawa, he moved to Malaysia to teach Biblical theology at the House of the Epiphany, the theological seminary of the Diocese of Kuching in Sarawak. When he returned to Canada, he was appointed to various parishes in West Quebec and in the Ottawa area and served as the Archdeacon of West Quebec and of Carleton until 1990, when he became the rector of Christ Church Cathedral and the Dean of Ottawa. In 1999 he was ordained a bishop and became the eighth bishop of Ottawa on September 1, 1999, a role in which he continued until 2007. In 2004 he was appointed as Bishop Ordinary to the Canadian Forces; and chaired the Interfaith Committee on Canadian Military Chaplaincy. He was succeeded as Bishop Ordinary by Nigel Shaw on May 28, 2016.