Mix together: ground meat, milk, ketchup, salt, pepper and the egg.
Add the breadcrumbs, mustard, onion and worcestershire sauce, mixing well.
Mix the tomato sauce, vinegar, chili powder and brown sugar together.
Clean the peppers, cutting the stems off and cleaning out the seeds.
Coat the in-side of the peppers with sauce.
Fill the peppers with meat and place up-right in a casserole dish.
Spoon the sauce over top of peppers until covered but don't use all sauce.
Bake for 1 to 1-1/2 hrs. at 350ºF, basting with sauce during cooking.
Serve with rice and warmed up remaining sauce.