Preheat oven to 350°F.
Wash all bell peppers. Slice in half vertically, remove seeds, and lay in a baking dish.
Chop onion and spinach. Cook bacon as directed on package until crispy. Cool, crumble, and set aside.
Whisk together eggs, milk, salt, onion, spinach, and bacon. Pour an even amount into each pepper, then sprinkle with cheese.
Bake for 45-50 minutes until eggs have set and are no longer runny.
Serve with orange wedges on the side.