Primarily a goal-kicking fullback or five-eighth, during his 14-year top-grade career he played with several clubs in both Australia and England, which included two NSWRL premierships, a Challenge Cup victory as well as state and national representative honours.
[5] O'Neill was signed to a sporting scholarship with the Brisbane Broncos at age fifteen and was selected for the Australian Schoolboys side in 1989 and 1990.
However, he was ruled ineligible to play for this representative side in 1990 due to having already been a non-playing bench player for the Brisbane Broncos in a match against St George while O’Neill was still in Year 12.
O'Neill briefly signed for English club Widnes,[7] who were then coached by Phil Larder and he appeared as a substitute in the 1993 Challenge Cup Final at Wembley Stadium, only to suffer a 20–14 defeat by Wigan.
The Broncos reached the 1993 Winfield Cup Grand Final and O'Neill played at fullback as they again beat St. George for a second consecutive premiership title.
At Southport Magistrates Court in 1995 he faced five charges, following an incident at Conrad Jupiters Casino where he was reported to have urinated under a blackjack table, including indecent exposure and offensive behavior.
O'Neill set club records for most tries and goals in a match but was released by the Reds 9 rounds into 1997 after multiple off-field incidents including phoning teammates and asking for money during a late night gambling session.
In 1998, however he suffered immense publicity and a $10,000 fine from the club over a 1999 pre-season tour incident where a drunken O'Neill defecated in the footwear of teammate Jeremy Schloss.
[5][11] O'Neill returned to England the 2002 Super League season for the Wigan Warriors, enjoying victory in the Challenge Cup, until 2003 when he completed a mid-season move to the Widnes Vikings.
In 2004, while on a pre-season trip to Australia with the Widnes Vikings, he was accused of drunkenly attempting to set fire to a 13-year-old boy who was wearing a foam-rubber dolphin mascot suit whilst on a river cruise in Port Macquarie.
To avoid apprehension, O'Neill stripped to his underwear following the incident, dived into the Hastings River and swam to shore, before hitchhiking and being picked up by a passing car.