After coming through the ranks at Elite One Championship side Union Treiziste Catalane (the precursor to Catalan Dragons), Bosc was part of the Dragons' inaugural Super League squad and made his Super League debut against Castleford Tigers on February 26, 2006, in what was only the club's third Super League match. He spent most of 2006 as a fringe player, occasionally called upon to play at full-back. In 2007, with the arrival of Clint Greenshields, he was switched to the wing and enjoyed a successful campaign, albeit one curtailed by injury. With the retirement of Stacey Jones in 2008, Bosc was handed the opportunity to fill his considerable gap in the halves. He was a revelation in the role and went on to become a key player for the team, taking over the playmaking and goal-kicking responsibilities and setting a number of points-scoring records including becoming the first player to reach 1,000 points for the club.