Preheat your oven to 350 degrees.
In a large bowl, whisk together the egg and milk. Stir in the cheese, oats, onion and salt.
Crumble beef over the mixture and mix well. Shape into 8 loaves; place in a greased 13x9-in. baking dish
In a small bowl, combine the ketchup, brown sugar and mustard; spoon over loaves.
Bake, uncovered for 25-30 minutes.