Abstract: A motorized operator for moving a barrier, such as an upward acting garage door, between open and closed positions includes a support mounted adjacent one of a pair of barrier guide tracks or along a barrier counterbalance shaft and a drive mechanism mounted on the support and engaged with an elongated flexible member, such as a chain, cable or cog belt. A cog belt, for example, is connected to a drawbar connected to the barrier at one end and the belt is either connected directly to the barrier at the opposite end or to a storage reel supported for rotation on and with a shaft of a barrier counterbalance mechanism. The storage reel may include a spiral groove and be supported on the counterbalance shaft for axial translation to receive and dereel the belt as the barrier is moved between open and closed positions. One or more belt tensioning pulleys may be mounted on the support.