Preheat your oven to 350°F (175°C). Prepare your loaf pan by lightly greasing it or lining it with parchment paper.

In a large mixing bowl, combine the ground beef, chopped onion, beaten eggs, and milk. Add the breadcrumbs, minced garlic, ketchup, chopped parsley, Worcestershire sauce, and season with salt, pepper, and Italian seasoning. Mix gently until just combined.

Shape the mixture into a loaf that fits your prepared pan, ensuring even thickness.

For the glaze, whisk together the ketchup, brown sugar, and vinegar. Set aside half of the glaze.

Place the meatloaf in the oven and bake for 45 minutes. Brush the remaining glaze over the top and bake for an additional 15 to 30 minutes until cooked through.

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