In a large over-safe pan, heat oil over medium heat. Add the diced onions and saute for 2 minutes before adding garlic. Cook for another minute.
Add the ground beef along with the taco seasoning, dried oregano, and onion powder. Cook the ground beef, crumbling with a wooden spoon until mostly cooked through.
Add the salsa and mix to combine and cook for a minute.
Add the black beans and corn. And stir to combine.
Top the taco casserole evenly with shredded cheese.
Broil the taco casserole under high for 2 to 3 minutes, or until the cheese has melted. Alternatively, cover the pan and let the cheese melt.
Top the walking taco casserole with Fritos chips, shredded lettuce, sour cream, and sliced jalapeno (optional) before serving.