In a skillet over medium heat, sauté 2 cups of chopped spinach for about 2-3 minutes until wilted and vibrant. Squeeze out excess moisture and combine with 1 cup of crumbled feta, chopped sun-dried tomatoes, sliced black olives, and diced grilled chicken if desired. Mix well.

Lay a tortilla flat and spread a quarter of the filling on one half. Fold the tortilla over to form a half-moon shape and press down to seal. Repeat for remaining tortillas and filling.

In a non-stick skillet, heat 1 tablespoon of olive oil or butter over medium heat. Cook the first quesadilla for 3-5 minutes until golden brown, flip and cook the other side for another 3-5 minutes.

Remove quesadilla from skillet and rest for 1-2 minutes. Slice into wedges and serve warm with sour cream, salsa, or guacamole.