Preheat your oven to 350°F (175°C) and grease a loaf pan.

In a large mixing bowl, combine ground beef, quick oats, milk, eggs, onion, half of ketchup, salt, and pepper.

Transfer the meat mixture to the loaf pan and shape it into a loaf.

In a small bowl, whisk together remaining ketchup, brown sugar, and mustard for the glaze.

Spread half of the glaze over the meatloaf and bake for 45 minutes.

After 45 minutes, apply the remaining glaze and bake for an additional 15-20 minutes.

Let the meatloaf rest for 10 minutes before slicing and serving.