Place brisket in a large shallow dish or extra-large zip top bag; pour liquid smoke over brisket. Sprinkle evenly with onion, garlic salt and salt. Cover or seal, and chill 8 hours, turning occasionally.

Remove brisket and place on a large piece of heavy-duty aluminum foil, discarding liquid smoke mixture. Pour Worcestershire sauce evenly over brisket, and fold foil to seal; place wrapped brisket in a roasting pan.

Bake at 275-degrees for 5 hours. Unfold foil; pour barbecue sauce evenly over brisket. Bake 1 more hour, uncovered.