The control of an apparatus within a grain holding device for feeding grain to an unloader conveyor operable for conveying the grain from the holding device, includes sensing a predetermined condition or conditions representative of capacity of the unloader conveyor for receiving grain, and adaptively controlling the apparatus for feeding grain to the unloader conveyor in advantageous varying manners responsive to the conditions, including to delay initiation of feeding until the receiving capacity is increased, and to match the grain feed to the capacity. The automatic control can be overridden, to allow user control of unloader speed, and can be configured to allow cleanout of the unloader conveyor.