His Excellency Most Reverend Bishop W. T. McGrattan was born in London, Ontario. His Excellency received his undergraduate degree in Chemical Engineering at the University of Western Ontario, followed by a Master of Divinity from St. Peter’s Seminary in London. Bishop McGrattan was ordained to the priesthood in 1987 for the Diocese of London. Following three years of service with St. Joseph’s Parish in Chatham, Bishop McGrattan continued his studies in theology at the Pontifical Gregorian University in Rome, where he received a Licentiate in Fundamental Moral Theology in 1992. Bishop McGrattan served on the faculty of St. Peter’s Seminary in London as an associate professor, vice-rector, and dean of theology and was appointed as rector of the Seminary in 1997 He was ordained to the episcopate as Auxiliary Bishop of Toronto in 2009 and was appointed as Bishop of Peterborough, Ontario in 2014. His Excellency Most Reverend William McGrattan was installed as the 8th Bishop of Calgary on February 27, 2017.
Bishop McGrattan is a member of the Canadian Conference of Catholic Bishops; the CCCB Executive Committee; the Bishop Liaison for Catholic Health Alliance of Canada CHAC from 2011 to the present; a member of the CCCB Episcopal Commission for Evangelization and Catechesis; and a member of the Western Assembly of Bishops. Bishop McGrattan was the National Spiritual Director of the Catholic Women’s League of Canada CWL from 2013 to 2018 and the Chancellor of St. Mary’s University in Calgary.

He spoke on "Care for our Common Home - the Church at this Time", specifically in relation to sexual abuse in the church. The policies stated in "Protecting Minors" includes vulnerable adults. Bishops need to care for people (being shepherds first, and administrators second); Bishop McGratton makes it a priority to meet personally with those who want to speak with him.