In a large skillet, heat the olive oil over medium heat. Add the chopped spinach and sauté for 2-3 minutes until wilted.
In a mixing bowl, combine the sautéed spinach, feta cheese, mozzarella cheese, garlic powder, onion powder, salt, and pepper. Mix well.
Place one tortilla in the skillet over medium heat. Spread a quarter of the spinach and cheese mixture evenly over half of the tortilla.
Fold the tortilla in half and cook for 3-4 minutes until the bottom is golden brown. Flip and cook the other side for an additional 3-4 minutes until golden and the cheese is melted.
Remove the quesadilla from the skillet and repeat the process with the remaining tortillas and filling.
Cut each quesadilla into wedges and serve warm with sour cream or Greek yogurt on the side.