Career
West Bromwich Albion
O'Neil is a product of the West Bromwich Albion youth academy, having joined from Calor League club Histon as a youth player. In May 2012, O'Neil signed his first professional contract with the club. O'Neil then debuted for West Brom in a crucial 2–1 victory over Swansea City on 15 March 2014, and then went on to make two further appearances from the bench against Stoke City and Norwich City respectively.
He subsequently was rewarded for his progress with a new deal in May 2014, officially putting pen to paper on a one-year contract, plus a further year's option in the club's favour, on 1 July 2014. He made his Football League Cup debut on 24 September 2014 against Hull City, West Brom ended up winning the match 3–2. O'Neil's performance was praised by Manager Alan Irvine.
He made another appearance for West Brom in the Football League Cup against Bournemouth on 28 October 2014 though West Brom ended up losing the match 2–1. At the end of the 2014-15 season, O'Neil had his contract extended for another season. Loan spells
O'Neil gained professional experience during a loan spell at Finnish club VPS in summer 2012.
O'Neil quickly made an impact for the club in the first team and was named May's Team of the Month. O'Neil went on to make eighteen appearance for VPS before returning to England in early August. In late-November, O'Neil joined Football League One side Scunthorpe United on a one-month loan.
Making three appearance so far at the club earned O'Neil a loan extension until 13 January 2014. Soon after, O'Neil's loan spell with Scunthorpe United was soon extended until the end of the season. Chesterfield
On 24 August 2015, O'Neil joined League One side Chesterfield for an undisclosed fee.
Born in Cambridge, England, O'Neil says he is open to play for Wales national football team, as his mother is from Wales.