 O'Neill joined the Na Piarsaigh club at a young age and played in all grades at juvenile and underage levels, enjoying much championship success in the minor and under-21 grades.On 25 November 1990, O'Neill was just 16-years-old when he was a member of the extended panel of the Na Piarsaigh junior team that qualified to play Dromcollogher/Broadford in the Limerick Junior Championship final.He ended the game with a winners' medal following the 2-10 to 2-00 victory.