After ordination he was appointed to Japan where he would spend the following forty-five years apart from a four-year period on promotion work in Ireland between 1982 and 1986. He worked in all four Columban areas in Japan. His first appointments were in the Archdiocese of Osaka, to Yakatamachi, and Ryujin; in the Diocese of Fukuoka, to Obiyama, Oe and Hondo; then in the Diocese of Yokohama to Katase, Fujisawa, Ninomiya, and Hiratsuka; in the Archdiocese of Tokyo he worked briefly at Narita; finally he returned again to the Diocese of Fukuoka to spend his last seventeen years successively in Shimasaki and Tetori, both in Kumamoto City.
Willie had a very good command of both spoken and written Japanese. He had great interest in people and was a shrewd judge of character. He adopted a laid-back style that enabled him to mobilise the talents of lay persons and to motivate them to dedicate their talents to the Church. His kindness, sincerity, patience and generosity were deeply appreciated in his various appointments.
On his return to Ireland in 2005, he was asked to take charge of the Maynooth House. Most of his guests were Chinese priests, Sisters and seminarians who were taking courses in English and Theology. Willie was the perfect, welcoming, unobtrusive guest-master who made everyone feel at home and gave them the run of the house.