Cook the pasta in a large pot of salted boiling water for 8–10 minutes until al dente. Drain and set aside.

Sauté chopped onions and bell peppers in olive oil in a large skillet for 5–7 minutes over medium heat until softened.

Add cream of chicken soup, sour cream, garlic powder, onion powder, and milk, cooking while stirring until smooth and bubbling.

Combine cooked chicken and half of the Monterey Jack cheese into the creamy sauce, stirring until the cheese melts.

Fold the drained spaghetti into the creamy sauce mixture, ensuring even coating.

For a bubbly topping, transfer to a greased baking dish, sprinkle with remaining Monterey Jack cheese, and bake at 350°F for 20–25 minutes.

Let cool slightly, garnish with fresh parsley if desired, and serve warm.