McLennan is a 1975 graduate of both the Divinity School and the Law School, having obtained both degrees simultaneously. And in 1994, McLennan won the Divinity School's Katzenstein Award, which honors alumni for bringing together the disciplines of law and ministry.
From 1975 to 1984 he did legal ministry with the poor in the Dorchester section of Boston, an experience which caused him to develop many of his ideas about religion.
McLennan has served as the Tufts University Chaplain since 1984 and also lectures at Harvard Business School.