Add chopped onion and diced mushrooms to a pan with a little bit of water. Do not add a lot of water as the mushrooms will also release some water. Cook for about 5 minutes.
Add chopped zucchini, yellow squash and corn to the pan. Cook until the water evaporates (about 10 minutes).
Heat up the griddle to medium heat. Spread 2-3 tablespoons of queso (see link below) on two tortillas. Place one on the griddle and add the veggie mix.
Add the other tortilla on top and close the griddle.