Preheat the oven to 400°F.
In a large bowl, combine ground chicken, egg, breadcrumbs, milk, parmesan, salt, pepper, Italian seasoning, garlic powder, onion powder, and chopped parsley. Mix until just combined (don’t overmix).
Scoop and roll into about 25-30 meatballs (about 1½ tablespoons each).
Spread marinara sauce evenly in the bottom of the prepared baking dish. Place the raw meatballs directly into the sauce in a single layer.
Bake uncovered for 30 minutes, until the meatballs are cooked through.
Sprinkle mozzarella and parmesan evenly over the meatballs. Switch oven to broil and cook for 3–4 minutes, or until the cheese is melted, bubbly, and lightly golden.
Top with fresh parsley and serve warm.