Sauté onion in butter until soft. Combine with other ingredients and mix well. Form into loaf and place in 10"x14" baking pan. Pour 1/2 cup Barbecue Sauce (see below) over loaf and bake for 1 hour at 350 degrees F., basting from time to time with the remaining sauce.
1-1/2 cups tomato sauce
1/2 cup water
2 tablespoons vinegar
3 tablespoons brown sugar
2 tablespoons prepared mustard
2 teaspoons Worcestershire sauce
Combine all ingredients in saucepan and heat until well blended, stirring. Use as detailed above to baste meat loaf.