Preheat your oven to 375°F (190°C) and grease a baking dish.
In a large skillet, cook the ground beef over medium heat until browned and cooked through, breaking it apart with a spoon as it cooks.
Add the diced onion and bell pepper to the skillet with the ground beef, and cook for an additional 3-4 minutes until softened.
Stir in the black beans, corn, salsa, and taco seasoning, mixing until well combined. Cook for another 2-3 minutes to allow the flavors to meld together.
Spread half of the ground beef mixture evenly into the prepared baking dish. Sprinkle half of the shredded cheese over the top.
Repeat with the remaining ground beef mixture and shredded cheese, creating two layers.
Cover the baking dish with aluminum foil and bake in the preheated oven for 20-25 minutes, or until the cheese is melted and bubbly.
Remove the foil and bake for an additional 5-10 minutes, or until the cheese is golden brown and bubbly.
Remove from the oven and let cool for a few minutes before serving.
Serve the Mexican Casserole hot, garnished with your favorite toppings and accompanied by tortilla chips for dipping.
Recipe Notes and Variations
For a vegetarian version, omit the ground beef and add extra beans or vegetables.
Make it spicy by using hot salsa or adding diced jalapeños to the ground beef mixture.
Feel free to customize the toppings to suit your taste preferences. Guacamole, salsa, and sliced jalapeños are all delicious additions.