Recipe: BBQ Dinner (ribs, chicken and sausage) and a ? about it

I found this recipe in a Rochester, MI community cookbook while visiting relatives in Michigan last week. It does not say if you are to cover the casserole or not. I probably would, at least for most of the baking time. When there was 1/2 hour or so left, I would check the liquid level and probably remove the cover. Anyone else have any thoughts on that? I would like to make this for company, it appears to be an easy entertaining dish for fall or winter.

BBQ DINNER

3 lbs. pork spareribs, cut in 2-inch ribs
1 chicken, skinned and cut up
1 lb. sweet Italian sausage, cut into serving pieces
1 lb. hot Italian sausage, cut into serving pieces
3 large onions sliced into rings
SAUCE:
1 1/2 cups ketchup
1 1/2 cups water
8 Tablespoons sugar
3 Tablespoons Worcestershire sauce
1 Tablespoon salt
2 teaspoons paprika
1 teaspoon red pepper or Tabasco sauce
1/2 teaspoon chili powder
Salt and pepper to taste

Boil ribs 15 minutes then drain.

Place all meat in a large casserole dish and place onions between meat.

Combine all sauce ingredients and pour over meat.

Bake at 325 degrees F. for 4 hours.