Abstract: An envelope stacking apparatus adapted to be positioned at the end of a discharge conveyor for an envelope insertion machine, the apparatus including an infeed conveyor for picking up envelopes from the discharge conveyor, a stacking assembly for stacking envelopes, the stacking assembly including a stacking conveyor and a pusher plate, a transfer conveyor for transferring the envelope stacks from the stacking assembly, a drive mechanism for driving the infeed conveyor and transfer conveyor continuously, the drive mechanism including a one-revolution clutch for intermittently actuating the stacking conveyor and a counter for tripping the clutch when a predetermined number of envelopes have been stacked in the stacker assembly.