As a scrum-half, O'Neill gained his solitary Ireland cap against Scotland at Inverleith during the 1920 Five Nations Championship. He captained the Queen's University first XV and also played rugby for Collegians.[2]
O'Neill was a rugby writer for the Belfast News-Letter, under the pen name "Criticus".[1]
A civil servant, O'Neill worked in the Ministry of Home Affairs for many years and was put in charge of settling the World War II evacuees from Holland, after Germany invaded. He became assistant secretary of the ministry.[2]