O'Brien featured in the pre-season game against the Dewsbury Rams. O'Brien was not selected in any league or cup matches this season. At the end of the 2010 season he was given a 3-year professional contract.
2011
O'Brien featured in three of the four pre-season friendlies. He played against Halifax, the Dewsbury Rams and the Keighley Cougars. O'Brien made his Super League début against the Huddersfield Giants, however he was not selected until later against the Hull Kingston Rovers and played until the match against Wakefield Trinity Wildcats. He did feature in the Challenge Cup game against Halifax.
2012
O'Brien featured in three of the four pre-season friendlies. He played against the Castleford Tigers, the Dewsbury Rams and Hull F.C. O'Brien featured in Round 19 to Round 21. He signed a 5 Year Extension to his contract midway through the season.
2013
O'Brien featured in the pre-season friendlies against the Dewsbury Rams and the Leeds Rhinos. He featured in Round 5 and then in Round 7. O'Brien also featured in Round 10 and Round 17. His next appearance was in Round 25 to Round 27. O'Brien featured in the Challenge Cup against Rochdale Hornets. He scored a try against Huddersfield Giants.
2014
O'Brien featured in the pre-season games against Hull FC and Castleford Tigers. He featured in Round 1 to Round 14 then in Round 16 to Round 27. Adam featured in Round 4 to the Quarter Final in the Challenge Cup. He scored against the Wakefield Trinity Wildcats, the Huddersfield Giants, Oldham, the Salford Red Devils and the Hull Kingston Rovers. O'Brien re-signed with the Bradford Bulls for another 2+Years despite their relegation to the Championship for the 2015 season.
2015
O'Brien featured in the pre-season friendlies against the Castleford Tigers and the Leeds Rhinos. He featured in Round 1 to Round 23. O'Brien played in Qualifier 1 to Qualifier 6. Adam played in the £1 Million Game. He also featured in the Challenge Cup in Round 4 to Round 5. He scored against Leigh Centurions, Featherstone Rovers, Hunslet, London Broncos and Hull Kingston Rovers. At the end of the 2015 season O'Brien won the T&A player of the year, the Bradford members player of the year and Bradford Players' player of the year.
2016
O'Brien featured in both pre-season friendlies against the Leeds Rhinos and the Castleford Tigers. He scored against the Leeds Rhinos. He featured in Round 1 to Round 22. Adam played in the Championship Shield Game 1 to the Final. He scored against Whitehaven, the Leigh Centurions, the Dewsbury Rams, Workington Town, Oldham, the Swinton Lions and the Sheffield Eagles. Midway through the season O'Brien signed a contract extension keeping him at the club until the end of 2019.
Dewsbury Rams
O'Brien was dual registered with Dewsbury for the 2013 season. He featured against Doncaster, Featherstone Rovers, Hunslet, Whitehaven, York City Knights, Workington Town, Sheffield Eagles, Keighley, Halifax and Swinton. He scored against Doncaster, York City Knights, Swinton, Sheffield Eagles and Halifax.
Huddersfield Giants
Following Bradford's liquidation prior to the 2017 season, O'Brien signed a 3-Year Deal following teammate Alex Mellor to the Huddersfield Giants of the Super League.
