Preheat the oven to 350°F (175°C) to prepare for baking.
Cook the spaghetti according to the package instructions until it reaches an al dente texture. Once cooked, drain thoroughly and set it aside to cool slightly.
In a large mixing bowl, combine the shredded chicken, cooked spaghetti, diced green bell peppers, diced red onion, cream of chicken soup, sour cream, chicken broth, garlic powder, onion powder, and a generous pinch of salt and pepper. Stir well until all ingredients are evenly mixed.
Lightly grease a 9x13-inch baking dish with non-stick spray or a drizzle of olive oil to prevent sticking. Carefully pour the chicken and spaghetti mixture into the dish, spreading it out evenly with a spatula.
Generously sprinkle the shredded Monterey Jack and cheddar cheese over the top of the mixture, ensuring complete coverage for a melty, cheesy finish.
Cover the baking dish tightly with aluminum foil to lock in moisture, and place it in the preheated oven. Bake for 25 minutes.
After 25 minutes, carefully remove the foil and return the dish to the oven. Bake for an additional 10-15 minutes, or until the cheese is melted, bubbling, and golden brown.
Once the baking time is complete, carefully remove the dish from the oven and allow it to cool for 5-10 minutes; this helps it set slightly for easier serving.
Before serving, garnish with freshly chopped parsley to add a burst of color and freshness to the dish.
Notes
Consider serving the bake directly from the dish and accompany it with a simple green salad for a complete meal.