Preheat oven to 350 degrees. Spray a 9x9 baking pan with non-stick spray.
Brown ground beef with onion, when it's almost done, add in the can of green chiles. Finish browning. Drain any excess grease. Add in taco seasoning and water, simmer. Stir in chopped bell pepper.
Add crushed Doritos to the bottom of the dish, spread evenly. Top with meat mixture.
Add shredded cheese.
Bake uncovered 20 minutes or until heated through and cheese is nice and bubbly.