Trim the a thin slice off the side of the whole, unpeeled onion. Set the onion flat on the cut surface for stability. Cut the onion into 4 (1-inch thick) slices. Remove the outer ring of skin from each slice. Drizzle the sliced onion with light colored oil and season both sides with steak seasoning or salt and pepper, to taste. Grill on hot grill or on a nonstick griddle for 5 to 7 minutes on each side until onion is tender and has begun to caramelize.