Preheat your oven to 350°F (175°C) and prepare a loaf pan or a rimmed baking sheet.

Combine the ground beef, diced onion, eggs, milk, breadcrumbs, minced garlic, ketchup, chopped parsley, Worcestershire sauce, salt, pepper, and Italian seasoning in a large mixing bowl.

Shape the mixture into a loaf and place it in the prepared pan.

Prepare the glaze by mixing ketchup, brown sugar, and mustard, then brush half over the meatloaf.

Bake in the preheated oven for about 45 minutes.

Check for doneness; the internal temperature should reach 160°F (71°C).

Let the meatloaf rest for 10-15 minutes before slicing.

Slice and serve warm, ideally with mashed potatoes or salad.