A broadcast spreader assembly for spreading granular material over a yard, field, or the like includes a hopper for holding granular material, a motor for driving a rotating drive shaft having a distribution chamber in a side of the rotating drive shaft, and a spreader mechanism. The rotating distribution chamber delivers a constant dosage of granular material to the spreader mechanism with each rotation thereof. The broadcast spreader may be remotely controlled by software on a smart phone, tablet or other computing device, and the rotational speed of the drive shaft and distribution chamber may vary in accordance with the ground speed of the broadcast spreader, in order to administer the proper dosage of granular material to a specific area or acreage of land. The broadcast spreader assembly is attachable to a spreader mechanism, such as a lawnmower or blower, or the like.