After studies at Mount St Mary's Seminary, Greenmeadows and a period as a Marist Brother,[2] he was professed as a member of the Society of Mary on 7 January 1969 and ordained a priest by Bishop John Mackey at Frankton on 29 June 1975.

[3] After ordination, Donoghue taught for some time at St Bede's College, Christchurch, before joining the Marist Oceania province.

When he was appointed Bishop of Rarotonga he was the Provincial Superior of the Oceania province (2006–2011).

The principal co-consecrators were Archbishop Charles Daniel Balvo (Nuncio to the Cook Islands) and Bishop Denis George Browne of Hamilton (also a predecessor in Rarotonga).

[2] Donoghue's retirement from the Bishophric of Rarotonga became effective on 29 June 2024, the same day he would become the Principal Consecrator of his successor, Bishop Reynaldo Getalado MSP.