Preheat the oven to 450° F. Line a large baking sheet with parchment paper and set aside.
In a large bowl, combine the ground turkey, breadcrumbs, chopped spinach, grated onion, minced garlic, crumbled feta, red wine vinegar, oregano, mint, parsley, egg, salt, and pepper. Stir well with your hand or a wooden spoon until combined.
Form and shape the meatballs into 1 1/2 inch meatballs and place them on the baking sheet. Brush with olive oil just before baking.
Bake the meatballs for 20 to 25 minutes
Meanwhile, heat a large skillet over medium-high heat and add the olive oil and the diced onion. Cook until soft and translucent, about 2-3 minutes. Add the minced garlic and cook until fragrant.
Add the orzo pasta and the water or broth to the skillet and bring to a boil. Reduce to a simmer and cook until the liquid is absorbed for about 12 minutes. Add the feta cheese, chopped spinach, lemon zest, and juice of one lemon to the orzo and stir until the spinach is wilted and everything is combined. Season with salt and pepper to taste.
Serve the meatballs over the orzo and pair them with a simple Greek salad, tzatziki sauce, and toasted pita bread if desired.