Heat olive oil in a skillet over medium heat. Sauté red onion and garlic until softened. Add spinach and cook until wilted. Season with salt, pepper, and oregano.

In the same skillet, place one tortilla, sprinkle half the mozzarella, add the spinach mixture, feta, and top with remaining mozzarella. Place another tortilla on top.

Cook for 4-5 minutes on each side until golden brown and cheese is melted. Use a spatula to flip carefully.

Slice into wedges and serve warm.