Preheat the Oven

1. Preheat your oven to 375°F (190°C).
2. Lightly grease a 9×13-inch baking dish with cooking spray or oil.

2. Cook the Chicken

1. Heat olive oil in a large skillet over medium-high heat.
2. Add chicken strips to the skillet and season with salt, pepper, and half the fajita seasoning.
3. Cook for about 5 minutes, stirring occasionally, until the chicken is golden brown and nearly cooked through.
4. Remove from the skillet and set aside.

3. Assemble the Casserole

1. In the prepared baking dish, layer the cooked chicken strips evenly.
2. Top with the sliced bell peppers and onion.
3. Sprinkle the remaining fajita seasoning over the vegetables.
4. Evenly distribute the shredded cheddar and mozzarella cheeses over the top.

4. Bake the Casserole

1. Cover the dish with aluminum foil and bake for 20 minutes.
2. Remove the foil and bake for an additional 10 minutes, or until the cheese is melted, golden, and bubbly.

5. Garnish and Serve

1. Sprinkle chopped cilantro over the casserole for a fresh, bright finish.
2. Serve hot with your choice of sour cream, guacamole, or salsa. Pair with rice, tortillas, or chips for a complete meal.