Pulse onions and garlic in food processor until finely chopped.
Combine remaining ingredients, except bacon and gravy, and blend well.
Form meat mixture into a long flat loaf.
Place loaf on wire or perforated rack set in roasting pan above about 1 in water, wrap loaf with bacon strips.
Bake until bacon is crisp and meat is at 155°F, about 45 min.
Gravy: Remove drippings and allow fat to rise. Add 2 T fat to 2 T flour and cook over medium heat about 5 min. Add 1 C drippings with stirring and heat until thickened.