Preheat oven to 350 degrees. Melt butter in a large casserole. Saute onions 2 minutes over medium heat. Add mushrooms and saute 5-7 minutes more. Add barley. Cook until lightly browned. Add 2 cups of broth, salt and pepper. Bring to a boil. Cover, reduce heat, and bake 45 minutes. Add remaining 1 cup of broth. Return to oven and bake 30 minutes more. Garnish with chopped parsley. SOURCE: National Cooking Echo 04/19/90 Contributed to the echo by: Ellen Cleary