Fr. John W. Grennon OCD was born in Springfield, MA on August 31, 1946. He was professed as a Discalced Carmelite Friar on May 1, 1991. On May 24, 1997, he was ordained to the priesthood at the Basilica of the National Shrine of Mary Help of Christians at Holy Hill in Hubertus, WI.

Fr. John served as a Secular Order Delegate for the Washington Province. He was assigned to Holy Hill to serve with the Hispanic ministry, at Holy Espousal Monastery in Brighton, MA, and the Sacred Heart Monastery (St. Florian Parish in Milwaukee, WI). He ministered to the residents at Mitchell Manor and Sacred Heart Care Center of the School Sisters of St. Francis.