Lay out two tortillas. Sprinkle each with mozzarella and feta, then evenly distribute the spinach mixture over the cheese. Top with the remaining tortillas.
Heat a clean skillet over medium heat and lightly grease with cooking spray or oil.
Cook each quesadilla for 2–3 minutes per side, or until golden brown and cheese is melted.
Remove from skillet, let rest for a minute, then slice into wedges and serve.
Notes
Use frozen spinach (thawed and drained) if fresh is not available.
Add sun-dried tomatoes or olives for extra Mediterranean flavor.