 Collins was ordained a priest for the Diocese of Hamilton, ON by Bishop Paul Reding on 5 May 1973.He then served as associate pastor at Holy Rosary Parish in Burlington and at Christ the King Cathedral, as well as an English teacher and chaplain at Cathedral Boys' High School.He furthered his studies in Rome, specializing in sacred scripture at the Pontifical Biblical Institute, from which he obtained a Licentiate in Sacred Scripture in 1978.