Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper.

In a large bowl, combine the breadcrumbs and milk and let them soak for a few minutes.

Add ground beef, egg, grated Parmesan, minced garlic, onion, chopped parsley, salt, and black pepper to the soaked breadcrumbs. Gently mix everything until just combined.

Roll the mixture into meatballs, about 1 to 1.5 inches in diameter, and place them on the prepared baking sheet.

Lightly brush the tops of the meatballs with olive oil.

Bake for 18–22 minutes or until fully cooked and golden brown. Let rest briefly before serving.