Williams served two terms as Dean at the Aberystwyth and Lampeter School of Theology (1985-1987 and 1994-1997), and was Visiting Professor at Acadia Divinity College, Acadia University in Nova Scotia in 1997. He sat on the translating panel for the New Testament section of Y Beibl Cymraeg Newydd (The Revised New Welsh Bible) from 1975 onwards and was secretary of the Theological Branch of the University of Wales's Guild of Graduates for 36 years. He also served as chief A level examiner in Religious Studies for the WJEC for twelve years.