In a large mixing bowl, combine egg, oats, milk, tomato juice, onion, the 1 tablespoon ketchup, the 1 teaspoon mustard, salt, and pepper. Add the ground meat and mix well. Press into an ungreased 7-1/2x3-1/2x2-inch loaf pan. Cover with foil.
Place the loaf pan in a larger pan. Fill the large pan with water to a depth of 1 inch. Bake the meat loaf in a 350 degree F oven for about 30 minutes.
Stir together the 1/3 cup ketchup, brown sugar, and 2 teaspoons mustard.
Remove foil from the pan. Spread topping over meat loaf. Bake for 30 to 45 minutes more or until no pink remains. Transfer meat loaf to a serving platter. Let stand for 10 minutes before slicing. Makes 6 servings.