Start by preheating your oven to 350°F (175°C).
In a large mixing bowl, combine the cooked, shredded chicken, diced bell peppers, diced onion, corn, salsa, garlic powder, onion powder, cumin, black pepper, and salt. Mix everything well until fully combined.
Spread a thin layer of the chicken mixture on the bottom of your greased 9x13-inch baking dish. Then, place 4 flour tortillas over the mixture, covering it completely.
Sprinkle half of the shredded cheddar and Monterey Jack cheese over the tortillas.
Add another layer of the chicken mixture over the cheese, followed by the remaining tortillas. Top with the rest of the chicken mixture and finish with the remaining cheese.
Cover the baking dish with aluminum foil and bake for 20 minutes. After that, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden brown.
Once out of the oven, let your Cheesy Chicken Quesadilla Bake cool for a few minutes. Garnish with fresh cilantro, if desired, and serve warm.