In a large mixing bowl, combine the ground turkey, Italian-style breadcrumbs, grated Parmesan cheese, beaten egg, minced garlic, grated onion, chopped fresh parsley, dried oregano, and salt and pepper to taste. Mix gently until just combined.

Scoop out portions of the turkey mixture and roll them into balls about 1.5 inches in diameter. Place the formed meatballs on a baking sheet lined with parchment paper.

Heat olive oil in a large skillet over medium-high heat. Once shimmering, add the meatballs in batches and sear for about 5 minutes, turning occasionally until browned on all sides.

In a medium baking dish, pour marinara sauce to cover the bottom. Arrange the seared meatballs on top and spoon more marinara over them. Bake in a preheated oven at 400°F for 18-20 minutes until the internal temperature reaches 165°F.

Remove from oven and let rest for a few minutes. Serve hot, garnished with additional grated Parmesan cheese and chopped parsley.