 O'Keefe was assigned to the Cathedral of St. Paul and served briefly as a teacher at St. Thomas Military Academy in St. Paul, after which he served the archdiocese as vice chancellor and then chancellor.He also served as chaplain to a convent of Benedictine nuns.On June 14, 1957, Pope Pius XII named O'Keefe a Domestic Prelate with the title Monsignor.