Upon his return from military service, Hollis earned an M.A. from Balliol College, Oxford. He then went to the Venerable English College in Rome, where he was ordained a priest for the Diocese of Clifton on 11 July 1965, and subsequently received a Licentiate of Sacred Theology (STL). In 1981 he was appointed Administrator of Clifton Cathedral in Bristol and Vicar General of the Diocese of Clifton. While still in this post, he was appointed a member of the IBA's panel of religious advisers and in 1986 became a member of the Central Religious Advisory Committee (CRAC) for the BBC and the IBA. In February 1987, Hollis followed in the family footsteps when, like his grandfather and his uncle, he was appointed as auxiliary bishop (known as a "suffragan bishop" in the Church of England) to Archbishop Maurice Noël Léon Couve de Murville of the Archdiocese of Birmingham. Hollis was given special responsibility for the Oxfordshire area. This was not to last, for he was installed as Bishop of Portsmouth on 27 January 1989. Hollis has been Chairman of the Catholic Media Trust and also Chairman of the Bishops' Committee for Europe. He served as a member of the Pontifical Council for Social Communications in the Vatican, as Chairman of the Bishops' Conference Department of Mission and Unity, Representative for the Bishops' Conference of the Churches Together in Britain and Ireland and a Member of IARCCUM (International Anglican Roman Catholic Committee for Unity and Mission). He is said to enjoy cricket and golf and, in the family tradition, to take a keen interest in current affairs. Holy Trinity Monastery, East Hendred, a monastery of contemplative Benedictine nuns situated in the Vale of White Horse, Oxfordshire, and part of the Roman Catholic Diocese of Portsmouth was founded by Hollis in 2004. In 2011, aged 75, Hollis announced that he would be retiring as soon as a replacement could be found. On Tuesday 11 July 2012, an official press release from the Vatican Information Service (VIS) of the Holy See Press Office stated that Pope Benedict XVI had named Philip Egan, the Vicar General of the Roman Catholic Diocese of Shrewsbury, as Bishop-Elect of Portsmouth. Egan was consecrated as the Eighth Bishop of Portsmouth, with Bishop Hollis serving as Principal Consecrator, on 24 September 2012, the Feast of Our Lady of Walsingham.