Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a mixing bowl, combine the ground beef, breadcrumbs, milk, Parmesan cheese, egg, chopped onion, minced garlic, dried Italian herbs, salt, and pepper.
Using your hands or a spoon, mix the ingredients until well combined, but do not overmix.
Shape the mixture into 1-inch (2.5cm) meatballs and place them on the prepared baking sheet, spacing them about an inch apart.
Bake in the preheated oven for 20 minutes, or until the meatballs are browned and cooked through (internal temperature should reach 160°F or 70°C).
While the meatballs are baking, heat the marinara sauce in a small saucepan over low heat.
Serve the meatballs warm with the marinara sauce for dipping.