He received his episcopal consecration on the following 10 April 1983 from Cardinal Tomás Ó Fiaich, with Archbishop Gaetano Alibrandi and Bishop Cahal Daly as co-consecrators.
Widely seen as pastorally sensitive and displaying an empathy for people given his parish as opposed to academic experience he generally adopted a low-profile approach to his episcopal ministry but did some wider work within the Irish Bishops Conference.
[6] A 2011 investigation into the handling of child sex abuse allegations stated that Bishop O'Reilly "displays a gentle caring approach but with great wisdom and honesty," and further that he along with the diocese's designated person in the area of child safeguarding, "ensures that allegations are addressed in full.
"[7] On 17 July 2013, Bishop O'Reilly's resignation from the pastoral government of the Diocese of Ardagh and Clonmacnoise was accepted by Pope Francis, in accordance with the 1983 Code of Canon Law.
[9] Once there, O'Reilly allegedly made McDonnell tell him everything that he had told the local police, before making him kiss his ring and swear to never to tell the story again.