Preheat the oven to 375°F. Spray a 9x13-inch baking dish with nonstick cooking spray. Set aside.

Place the black beans, pinto beans, kidney beans, corn, scallions, bell pepper, salsa, cumin, chili powder, oregano, garlic powder, and salt in a large mixing bowl. Mix with a rubber spatula to combine.

Arrange half of the chips in an even layer in the prepared baking dish. Top with half of the bean mixture. Sprinkle evenly with half of the shredded pepper jack and cheddar cheeses. Repeat with remaining chips, beans, and cheeses.

Bake the casserole on middle rack of oven until cheese is melted and lightly browned on top, 23-27 minutes.

Check to see that casserole is done. Remove from oven or add time as needed.

Serve immediately, topped with sour cream and diced avocado if desired.