Preheat oven to 350°F. Grease a 9"x13" casserole dish.
Brown ground beef and onions, drain fat. Stir in taco seasoning, chili powder, and water.
Bring to a boil, reduce heat and simmer until thickened. Stir in diced tomatoes, tomato sauce, corn, & beans. Simmer an additional 5 minutes.
Add 4 cups of Frito chips to the bottom of prepared dish. Sprinkle with 1 cup of cheese.
Spread beef mixture over top and top with remaining cheese.
Bake 18 to 20 minutes or until cheese is melted.
Top with remaining chips and desired toppings.
