Preheat your oven to 350°F (175°C). Line a baking sheet with aluminum foil and lightly grease it, or use a loaf pan.
Mix Meatloaf Ingredients:
In a large bowl, soak the bread crumbs in milk for a few minutes. Add the beaten egg, chopped onion, minced garlic, Worcestershire sauce, ketchup, thyme, parsley, salt, and pepper. Stir until well combined.
Add the ground beef to the mixture. Mix gently with your hands or a fork until just combined. Avoid overmixing to keep the meatloaf tender.
Shape the Meatloaf:
Transfer the meat mixture to the prepared baking sheet and shape it into a loaf, or press the mixture into the loaf pan.
Prepare the Glaze:
In a small bowl, mix together the ketchup, brown sugar, mustard, and vinegar until smooth.
Bake:
Spread about half of the glaze over the top of the meatloaf before baking.
Bake in the preheated oven for about 1 hour, or until the internal temperature reaches 160°F (71°C). Baste occasionally with the remaining glaze during the last 15 minutes of cooking.
Rest and Serve:
Let the meatloaf rest for 10 minutes before slicing. This helps retain its juices.
Serve slices of meatloaf with the remaining glaze on the side or drizzled on top.
