Clean the potatoes; peel and cut into slices about 1/4-inch thick.
Combine margarine, honey, and cinnamon in a small bowl; stir until smooth.
Coat the grill with cooking spray and preheat for 5 minutes. Place the potato slices on the grill and cook for 3 minutes. Spoon the honey butter over the potatoes and grill for an additional 4-6 minutes.
Place the grilled potatoes on a serving platter and drizzle with the melted honey butter.