Step 1

Preheat the oven to 375 degrees F.

Step 2

Spray a 9x9-inch or 11x7-inch baking dish with nonstick cooking spray.

Step 3

In a large skillet over medium heat, add the ground beef and the onion.

Step 4

Cook while crumbling until the meat is no longer pink, about 7-10 minutes.

Step 5

Drain the grease from the skillet.

Step 6

Add the tomatoes, chili beans, and taco seasoning to the meat mixture.

Step 7

Bring the mixture to a simmer and allow it to simmer for 5 minutes.

Step 8

Transfer the mixture to the prepared baking dish.

Step 9

Top the mixture with the corn chips and cheese.

Step 10

Cover the casserole with foil and bake for 20 minutes.

Step 11

Carefully discard the foil and bake until the cheese is melted and the top is slightly golden, for about 5-10 minutes.

Step 12

Carefully take the casserole out of the oven and top with the lettuce, diced tomatoes, olives, sour cream, and avocado.

Step 13

Serve.