In a large mixing bowl, combine the ground turkey, finely chopped spinach, breadcrumbs, grated Parmesan cheese, chopped onion, minced garlic, egg, dried oregano, salt, black pepper, and red pepper flakes (if you're adding the kick). Use your hands to mix all the ingredients together until well combined. Be careful not to over-mix, as this can make the meatballs tough.
Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper to prevent sticking and for easy cleanup.
With slightly wet hands (to prevent sticking), form the turkey mixture into meatballs about 1 to 1.5 inches in diameter. Place each meatball on the prepared baking sheet, ensuring they are spaced apart for even cooking.
Bake the meatballs in the preheated oven for approximately 20 minutes, or until they are fully cooked through and boast a nice golden-brown color on the outside.
Meanwhile, while the meatballs are baking, heat the olive oil in a large skillet over medium heat. Pour in the marinara sauce and let it simmer gently until warmed all the way through.
Once the meatballs are baked to perfection, transfer them to the skillet with the marinara sauce. Gently toss the meatballs in the sauce to coat them well. Allow them to simmer together for an additional 5 minutes to meld the flavors.
Serve the meatballs hot from the skillet, garnished with extra grated Parmesan cheese and fresh basil leaves if desired for a burst of flavor and color.
Notes
These meatballs pair wonderfully with whole-grain pasta, zoodles, or a side of garlic bread.