1. Place the brisket in a glass shallow dish; pour the liquid smoke over the brisket then rub all over with fresh garlic.
2. Place the onions on and around the brisket.
3. In a small bowl mix together the garlic salt, white salt, cayenne pepper and black pepper, then sprinkle the meat all over with the spice mixture.
4. Cover and refrigerate for 8 hours.
5. Remove the brisket and place on a large piece of heavy-duty foil, then discard the liquid smoke mixture.
6. Place the foil with the brisket on it in a large roasting pan, then pour the Worcestershire sauce evenly over the brisket.
7. Fold the foil up to seal tightly (prick a few small holes with a fork in the foil to allow the steam to escape).
8. Set oven to 275 degrees.
9. Bake for 5 hours.
10. Remove from oven and unfold the foil; pour the barbecue sauce evenly over the roast, return to oven UNCOVERED and cook for another hour at 275 degrees.
11. Delicious!