Grilled Summer Vegetable Quesadillas

small zucchini, sliced lengthwise into 1/4-inch thick slices

small summer squash, sliced lengthwise into 1/4-inch pieces

red, orange or yellow bell pepper, quartered with seeds and stems removed

anaheim pepper, quartered with seeds and stem removed

small red onion, sliced into 1/4-inch thick rounds

large Portobello mushroom, cleaned and sliced into 1/2-inch pieces

bunch asparagus, ends trimmed

bunch cilantro, chopped

olive oil

Kosher salt & freshly ground pepper

tortillas

freshly grated mozzarella cheese, divided

freshly grated pepperjack cheese, divided

Butter or oil for the pan