Heat oven to 450 deg. Place 2 tortillas on an ungreased cookie sheet. Sprinkle half the cheeses, onion, jalapeno, zucchini and corn on each. Season to taste with salt and pepper.
Place one of the two tortillas atop the other and the third tortilla atop the second. Transfer to the oven and bake until cheese has melted and tortillas are becoming crisp (about 10 min.).
Cut the quesadilla into quarters. Garnish with salsa, avocado slices, sour cream, or whatever else you like. Serve hot.
From the Dinner Co-op