Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a large mixing bowl, combine the ground turkey, finely chopped spinach, feta cheese, breadcrumbs, Parmesan cheese, minced garlic, oregano, salt, pepper, and the egg.
Mix all the ingredients well with your hands or a spoon until evenly combined.
Using your hands, form the mixture into meatballs, about 1.5 inches in diameter, and place them on the prepared baking sheet.
Drizzle a little olive oil over the meatballs to help them brown during cooking.
Bake in the preheated oven for 20-25 minutes or until the meatballs are cooked through and golden brown on the outside.
If desired, warm up marinara sauce in a small saucepan and serve it on the side for dipping or drizzling over the meatballs.
Enjoy your delicious turkey meatballs warm as an appetizer or a main dish!