01 - Set oven to 350°F (175°C) and prepare a standard loaf pan.
02 - In a large mixing bowl, thoroughly blend ground beef, breadcrumbs, milk, egg, diced onion, minced garlic, salt, and pepper until uniformly mixed.
03 - Form the meat mixture into a loaf and transfer gently into the prepared loaf pan.
04 - Whisk ketchup, brown sugar, and mustard in a separate bowl to create a smooth glaze.
05 - Evenly spread glaze over the meatloaf surface, place in oven, and bake for 60 minutes or until cooked through.
06 - Remove meatloaf from oven, rest for 10 minutes, then slice and serve warm.