Preheat oven to 400 degrees F.
Spray a 9x13-inch baking dish with nonstick cooking spray and set aside.
Heat the olive oil in a medium skillet pan over medium-high heat and saute bell peppers for 2-3 minutes.
Add the chicken, water, taco seasoning, corn, beans and tomato sauce to the pan and cook for about 5 minutes, stirring frequently. Remove from heat and set aside.
Prepare the corn muffin mix according to the package instructions and stir half of the French fried onions into the batter.
Pour the chicken mixture into the prepared dish and spread the cornbread batter on top.
Bake for 20 minutes, or until the cornbread topping is golden brown.
Top the casserole with the remaining onions and shredded cheese.
Bake for another 3-5 minutes or until the cheese has melted.
Remove the casserole from the oven and allow it to rest for a few minutes before serving.