Preheat oven to 350° F. Mix flour and pepper. Melt butter in saucepan. Add flour mixture. Cook over medium heat for one minute, stirring constantly. Remove from heat. Stir in milk. Return to heat and cook until thick. In a very large bowl, mix remaining ingredients with sauce. Place in lightly greased casserole dish. Cover and bake for 90 minutes. Re-move cover after 30 minutes. Let cool 15 minutes before serving.