1 small onion (sliced)
1 1/2 lbs. new white potatoes (scrubbed)
1/4 c. melted butter
1/2 tsp. salt
1/4 tsp. pepper
1/4 tsp. garlic salt
1/2 tsp. dried rosemary (optional)

Preheat grill or broiler. Spray a large piece of heavy-duty foil generously with cooking spray. Arrange onion slices in center of foil. Cut potatoes into halves; arrange cut sides up on onion slices. Drizzle butter over potatoes. Sprinkle with salt, pepper, garlic salt and rosemary. Fold foil to enclose vegetables and seal tightly. Grill or broil for 40 minutes, turning once. Open foil and fold back edges. Grill for additional 5 minutes or until potatoes are tender. Transfer to a serving dish.