Preheat oven to 275 degrees (135 degrees C).

Place roast in a large roasting pan and scatter chopped onions over.

In a large bowl, combine Worcestershire sauce, liquid smoke, garlic powder, salt and pepper. Pour in beer, stir and add to roasting pan. Add water to the top of beef.

Cover and cook in oven at 275 degrees F (135 degrees C) for 4 to 5 hours.

When meat is cooked, shred meat with 2 forks, add barbecue sauce and mix well.