Heat the oven to 375°F. Line a rimmed baking sheet with parchment paper.
In a large bowl, whisk the egg. Add the breadcrumbs, feta, spinach, red onion, garlic, oregano, salt, and black pepper. Stir to combine.
Add the ground turkey and mix gently with your hands or a fork until the ingredients are evenly distributed. Avoid overmixing so the meatloaf stays tender.
Shape the mixture into a compact loaf on the prepared baking sheet. Bake until the center reaches 165°F, about 40 to 45 minutes.
While the meatloaf bakes, stir together the Greek yogurt, lemon juice, lemon zest, dill, and parsley in a small bowl.
Let the meatloaf rest for 5 to 10 minutes after baking. Slice and serve with the lemon-herb yogurt glaze spooned over the top or on the side.