Melt butter in a cast iron Dutch oven; crumble brown sugar and add to melted butter. Add onions, peppers, vinegar and catsup. Simmer for 5 minutes.
Remove from heat; and pour barbecue sauce over chicken. Bake covered for 30 minutes at 325° F.
Uncover, baste and bake 30 minutes more, basting as needed. Raise temperature to 350° F for the last 15 to 20 minutes, basting frequently.Servings: 4