Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper to prevent sticking.
In a spacious mixing bowl, combine the ground turkey with the finely chopped spinach, crumbled feta cheese, breadcrumbs, grated Parmesan cheese, minced garlic, dried oregano, salt, black pepper, and the egg.
Using your hands or a sturdy spoon, mix all the ingredients together thoroughly until evenly blended; ensure the spinach and cheese are well distributed throughout the turkey.
With your hands, shape the mixture into meatballs about 1.5 inches in diameter and arrange them on the prepared baking sheet, leaving space between each meatball for even cooking.
Drizzle a small amount of olive oil over the meatballs to promote browning; alternatively, you can brush the oil on for a more even coating.
Bake in the preheated oven for 20-25 minutes or until the meatballs reach an internal temperature of 165°F (74°C) and are golden brown on the exterior.
If you like, gently heat marinara sauce in a small saucepan until warm, and serve it on the side for dipping or drizzling over the meatballs.
Relish your flavorful turkey meatballs while they're warm, either as a tasty appetizer or a satisfying main course!