Prep. Heat oven to 375F. Line a sheet pan with parchment (or lightly grease a loaf pan).
Sauté aromatics. Heat olive oil in a skillet over medium heat. Add onion and cook 5 minutes until softened. Add garlic and cook 30 seconds. Cool slightly.
Make the binder. In a large bowl, whisk eggs, milk, breadcrumbs, ketchup, Worcestershire, salt, pepper, and thyme. Let sit 2 to 3 minutes to thicken.
Mix. Add ground beef, sautéed onion/garlic, and parsley (if using). Mix gently with your hands just until combined.
Shape. Form into a loaf (about 10x5 inches) on the sheet pan. If using a loaf pan, press mixture in lightly without packing hard.
First bake. Bake 40 minutes.
Glaze. Stir glaze ingredients together. Spread glaze over the meatloaf and bake 10 to 15 minutes more, until the center reaches 160F.
Rest and serve. Rest 10 minutes, then slice and serve.