1. Preheat the oven to 350°F (175°C).

2. In a large bowl, mix together ground beef, breadcrumbs, onion, egg, milk, Worcestershire sauce, salt, and pepper.

3. Shape the mixture into a loaf and place it in a baking dish.

4. In a small bowl, mix together ketchup, brown sugar, and mustard to make the glaze. Spread the glaze over the meatloaf.

5. Bake in the preheated oven for 1 hour or until cooked through.

6. Let it rest for 10 minutes before slicing and serving.