An assembly is provided for moving the drive belt of a roller conveyor system between a first position in which the drive belt engages the rollers to rotate the rollers and a second position spaced from the rollers, the second position permitting conveyed articles to be accumulated on the rollers. The assembly comprises a bracket and at least one pulley having a circumferential groove for seating the drive belt. The pulley is rotatably secured to both the bracket and a first side frame for the conveyor. A guide roller is also secured to the bracket so as to maintain the drive belt seated on the pulley. At least one actuator is provided for our operating on the bracket to move the drive belt between the first and second positions.