Preheat your oven to 375°F (190°C) and lightly grease a standard 9x5 inch loaf pan with cooking spray or oil.

Place the thawed spinach in a clean kitchen towel and squeeze firmly to remove as much excess liquid as possible. This prevents the meatloaf from becoming soggy.

In a large mixing bowl, combine the ground turkey, squeezed spinach, crumbled feta, breadcrumbs, chopped onion, minced garlic, egg, oregano, salt, and pepper.

Mix the ingredients gently with your hands until they are just combined. Be careful not to overwork the meat, or the loaf may become tough.

Transfer the mixture into the prepared loaf pan and press it down evenly to smooth the top.

Bake in the preheated oven for 45 to 55 minutes, or until a meat thermometer inserted into the center reads 165°F (74°C).

Remove the meatloaf from the oven and let it rest in the pan for 10 minutes before slicing. This allows the juices to redistribute and keeps the slices intact.