Preheat oven to 350 degrees F. Shred or dice chicken into bite-size pieces.
Dice onion; drain and rinse beans. Place a clean skillet over medium heat; add oil and onion. Cook until softened, then add beans, chilies, corn, diced tomatoes and taco seasoning. Stir to combine and allow the mixture to begin to bubble.
Assemble lasagna: Spray an 8x8-in baking dish with cooking spray. Place one tortilla into dish and top with some of the vegetable mixture. Add some chicken and a small amount of cheese; repeat until all ingredients have been used, with the final topping being a tortilla with cheese on top.
Bake for 15 minutes or until cheese has melted. Serve hot with a dollop of sour cream on top.