1. Pre-heat barbecue for indirect heat to 350 degrees, either mounding charcoal on one side of grill only, or turning off one section of gas burners.
2. Chop bread into cubes and place in a large bowl.
3. Add the poultry spice, salt and pepper, and Worchestershire sauce and stir.
4. Sauté chopped onion in olive oil just until the onions turn translucent and soft.
5. Pour the onions and olive oil into the owl of bread cubes, add melted margarine, and stir.
6. Cut top ¼ from large onions and using a grapefruit spoon hollow out the onions so there is a nice sized hole in each one. I suggest leaving 2-3 layers of onion on the outside. Tightly pack each onion with stuffing.
7. Place each onion on a 12x12-inch square of aluminum foil, top with a pat of butter, and seal in foil.
8. Place foiled onions on the indirect (unheated side or portion) of the barbecue and cook at 350 degrees for 1 hour. Carefully remove foil and serve.