He played at representative level for Ireland and Lancashire, and at club level in the Super League for St. Helens, with whom he won a World Club Challenge, Challenge Cup and a Super League Grand Final, the Bradford Bulls (loan), the Salford City Reds (two spells, including the first on loan) and Harlequins RL, and the Leigh Centurions, the Swinton Lions and the Rochdale Hornets, as a fullback, wing, centre or second-row.
Having won the 1999 Championship, St. Helens contested in the 2000 World Club Challenge against National Rugby League Premiers the Melbourne Storm, with Stewart playing from the interchange bench in the loss.
As Super League V champions, St. Helens played against 2000 NRL Premiers, the Brisbane Broncos in the 2001 World Club Challenge.
Stewart played for St. Helens on the wing in their 2002 Super League Grand Final victory against the Bradford Bulls.
Having won Super League VI, St Helens contested the 2003 World Club Challenge against 2002 NRL Premiership-winners, the Sydney Roosters.