Preheat your oven to 350°F (175°C).
This temperature cooks the meatloaf perfectly.
Grease your loaf pan with cooking spray.
Put ground beef in a large bowl.
Add breadcrumbs, onion, eggs, and milk.
Add garlic, Worcestershire sauce, salt, pepper, and thyme.
Mix everything with your hands.
Don't overmix or meat gets tough.
Mix just until combined.
Put the meat mixture into your loaf pan.
Press it down gently but firmly.
Make the top smooth and even.
This helps it cook evenly.
Mix ketchup, brown sugar, and vinegar together.
Stir it in a small bowl.
The glaze should be smooth.
Spread half the glaze on top now.
Put the pan in your preheated oven.
Bake for 45 minutes without opening the door.
Then spread the remaining glaze on top.
Bake for 15 more minutes.
The internal temperature should reach 160°F.
Take the meatloaf out of the oven.
Let it rest for 10 minutes.
This keeps the juices inside.
Slice and serve warm.