Preheat oven to 375°F (190°C). Spray a 9X13 inch baking dish with nonstick cooking spray; set aside.
In a 12-inch skillet, brown the ground beef (1 pound) and onion (1 1/2 cups) until there is no longer any pink in the beef. Remove excess fat.
Stir in taco seasoning (1 envelope), green chiles (1 can) and its liquid, black beans (1 can), corn (1 bag), and enchilada sauce (1 can). Simmer the mixture over medium heat for about 10 minutes. Stir in 1 cup of sharp cheddar and 1 cup of Monterey jack cheese.
Spread the meat mixture into the prepared baking dish.
Arrange a layer of tater tots (1 bag) over the meat mixture. Bake, uncovered, in preheated oven for 35-40 minutes or until casserole is heated through.
Remove the casserole from the oven and sprinkle 1/2 cup sharp cheddar and 1/2 cup Monterey jack cheese on top. Return to oven and continue to bake until cheese is melted. Garnish as desired and serve.