Ku qor sii socodka faqradan - Kadib markii uu ka qalin jabiyay akadeemiyadda Connacht, O'Halloran waxaa la saxiixay qandaraas horumarineed xilli ciyaareedkii 2011-12. Xilli ciyaareedkaas ayaa Connacht u soo baxday koobka Heineken Cup, oo ah tartanka kooxaha ugu sareeya Yurub, markii ugu horreysay. 11-kii Nofeembar 2011, O'Halloran wuxuu dhaliyay isku daygii ugu horreeyay ee Connacht ee tartanka ka dhanka ah Harlequins wareegga furitaanka. Waxa kale oo uu u saftay Connacht guuldaradii 36/10 ee Toulouse iyo guuldaradii 23/19 ee Gloucester, isagoo dhaliyay isku day kale oo ka dhan ah Gloucester. O'Halloran ayaa markaas ciyaaray guuldaradii 24-3 ee ka soo gaadhay Toulouse laakiin wuxuu ciyaaray guushii ugu horeysay ee gobolka ee Heineken Cup markii Connacht uu ka adkaaday Harlequins 9-8. Sanadkii 2011<unk>12 Pro12
O'Halloran wuxuu dhaliyay isku day labada ciyaarood ee ay la ciyaareen Cardiff Blues oo ay weheliyaan isku dayyada Leinster iyo Glasgow Warriors. Wareegii 20aad ee ciyaaraha, O'Halloran wuxuu dhaliyay isku day guul ah oo 26 <unk> 21 ah oo ka soo gaadhay Ulster si uu u qaado tirada isku daygiisa shanta Pro12 iyo toddoba tartamada oo dhan.