Preheat your oven to 375 degrees.
Mix the ground beef, salt, pepper, onion, green peppers, egg, oats and diced tomatoes well. You may have to use your hands, but don't overwork the meat. Just until the ingredients are mixed in.
Form a loaf and place in a baking dish.
Mix ketchup, brown sugar and mustard together and spread over meatloaf.
Bake uncovered 1 hour, draining grease away twice by tipping the dish and using a spoon or holding the meatloaf with a spatula and draining straight from the dish.
Weight Watchers Points + estimated value (recipe is not endorsed by Weight Watchers): 3 points in 4 ounces. This recipe serves about 6.