[1] He signed for Oldham Athletic on a non-contract basis at the start of the 2003–04 season, which was extended for another month in September 2003 with the highlight being his last minute winner against Rushden and Diamonds in a 3-2 win.
[3] O'Halloran signed for King's Lynn in March 2005 following becoming disillusioned with professional football and became an integral part of the team that challenged for the Southern Premier league title where he was joined by former Boston United teammate Dean West.
[5] He was offered a new contract by manager Tommy Taylor but instead chose to sign for Corby Town where he scored on debut in the opening game of the season.
He left Corby at the end of the 2008–09 season and joined his home town club Lincoln United alongside former Boston and King's Lynn teammate Steve Melton becoming a regular on the scoresheet from midfield.
In October 2010, he joined Lincoln Moorlands Railway but persistent concerns with an ongoing back injury resulting in ruptured discs continued and he was forced to retire from competitive football at the age of 28.