Grilled Potato Fans

6 medium baking potatoes
2 medium onions, halved and thinly sliced
6 tbsp butter, cubed
¼ cup finely chopped celery
1 tsp salt
1 tsp dried oregano
¼ tsp garlic powder
¼ tsp pepper

With a sharp knife, make cuts 1/3 inch apart in each potato, leaving slices attached at bottom. Fan the potatoes slightly. Place each on a piece of heavy duty foil. Insert onions and butter between potato slices. Sprinkle with celery, salt, oregano, garlic powder and pepper. Fold foil around potatoes and seal tightly. Grill covered over medium-high heat for 40-45 minutes or until tender.