You can also use Old El Paso® flour tortillas for burritos, which are 8 inches in diameter.
If the 6-inch tortillas you're using are thick, use one 15-ounce can plus one 8-ounce can tomato sauce. When arranging tortillas in dish, cut 2 in half to fit, overlapping only if necessary. Bake covered 30 minutes. Uncover and bake 20 to 25 minutes longer.
If you like your food a little spicy, turn up the heat by using Monterey Jack cheese with jalapeño peppers rather than the Colby-Monterey Jack.
While the casserole bakes, fill small bowls with salsa, sour cream and chopped avocado so everyone can dress up this casserole to his or her taste.