 O'Donoghue came to Britain in 1959 to train for the priesthood first at Campion House, Osterley, Middlesex, then from 1961–67 at Allen Hall seminary when it was at St Edmund's, Ware.He was ordained to the priesthood for the Archdiocese of Westminster in England on 25 May 1967.He was appointed an Auxiliary Bishop of Westminster and Titular Bishop of Tulana on 18 May 1993.