Heat oven to 375°F.
Heat 4-quart saucepan over medium heat; add oil, then add squash, onion and chili. Cook about 3 minutes or until onions are softened.
Place tortillas on ungreased large cookie sheet; spread with salsa verde, then spoon on cooked vegetables. Top with cheese.
Bake 5 to 7 minutes or until hot and crispy around edges.