Mezue ahịrịokwu na-esonụ: Mgbe ọ gụsịrị akwụkwọ na Connacht academy, O'Halloran bịanyere aka na nkwekọrịta mmepe maka oge 2011<unk>12. N'oge ahụ, Connacht ruru eru maka Heineken Cup, asọmpi klọb kacha elu na Europe, na nke mbụ ya. Na 11 Nọvemba 2011, O'Halloran gbara agba nke mbụ nke Connacht na asọmpi ahụ megide Harlequins na agba nke mbụ. O sokwa Connacht merie ndị Toulouse na 36/10 na ndị Gloucester na 23/19, na-agbakwa mbọ ọzọ megide Gloucester. O'Halloran mechara gbaa bọọlụ n'asọmpị ha meriri Toulouse na 24-3 mana ọ gbara bọọlụ n'asọmpị Heineken Cup mbụ ha meriri mgbe Connacht meriri Harlequins na 9-8. N'ime
2011<unk>12 Pro12 O'Halloran gbara mbọ na egwuregwu abụọ megide Cardiff Blues tinyere mbọ Leinster na Glasgow Warriors. Na agba nke iri abụọ, O'Halloran gbara mbọ na mmeri 26 na 21 na Ulster iji were tally nke mbọ ya ise na Pro12 na asaa na asọmpi niile.