Heat the oil in a large skillet over medium-high heat.
Add the garlic, mushrooms and bell pepper.
Saute for 2-3 minutes.
Add the spinach and cook, stirring often, for 1-2 minutes or until the spinach is just wilted.
Spoon the vegetable mixture into a medium bowl.
Melt 1 t. of margarine or butter in the same skillet over medium high heat.
Add 1 tortilla; top with 1/2 vegetable mixture, 1/4 cup cheese and another tortilla.
Cook 1-2 minutes on each side, until lightly browned.
Repeat with the second quesadilla.
Cut into wedges and serve with salsa and light sour cream.