He played Division III college basketball for Post University in the United States in the early 2000s[1] and later represented the Irish national team as both a player and as a player-coach.
[2] On 26 March 2015, O'Reilly was named an inaugural Premier League All-Star First Pick alongside UCC Demons teammates Kyle Hosford and Lehmon Colbert.
[3] Three days later, he helped Demons create Irish basketball history by winning the Champions Trophy and adding to their undefeated 2014–15 season.
[7] On 22 June 2016, O'Reilly was appointed head coach of the Cheshire Phoenix for the 2016–17 British Basketball League season.
[22] O'Reilly was head coach of the Irish senior men's team from 2014 to 2016, helping them to a fourth-placed finish at the 2016 FIBA European Championship for Small Countries.