A slide-out or retractable room for a mobile living quarters, such as a recreational vehicle, is provided with actuating assemblies mounted on opposite side walls of the slide-out room and the adjacent wall of the main living area. The actuating assemblies include a pair of parallel gear racks mounted on the side wall, which are engaged by pinions rotated by torque shafts mounted on the main living quarters. Each torque shaft is rotated by a separate motor. A roller engages a bearing surface on the lower portion of the gear racks. Accordingly, the slide-out room is extended and retracted by rotating the torque shafts to cause the gear racks and the attached slide-out room to extend and retract. The weight of the slide-out room is supported by the rollers, thereby supporting the slide-out room off of the floor of the main living quarters as it extends and retracts. A synchronizing control operates the motors.