Preheat your oven to 400°F (200°C).

In a large mixing bowl, combine the ground beef, breadcrumbs, Parmesan cheese, chopped onion, minced garlic, parsley, salt, and pepper. Mix gently.

Using a cookie scoop, portion out the meat mixture to form even meatballs.

With damp hands, roll each portioned meatball to ensure they hold together.

Place the formed meatballs on a parchment-lined baking sheet and bake for 18–20 minutes or until they reach an internal temperature of 165°F (74°C).

Optionally, simmer the baked meatballs in marinara sauce for an additional 15–20 minutes.