Saute onion in the oil in a skillet for several minutes until tender, add garlic and saute for about one minute, add spinach and cook for several minutes until it starts to wilt
Drain mixture on paper towels
Combine cheeses and next 4 ingredients and mix well
Combine with spinach mixture
Spread mixture onto each tortilla
Fold tortilla over and press to seal along edges
Spray skillet with cooking spray and cook each quesadilla for several minutes on each side, remove and cut into quarters