01 -
Preheat the oven to 350°F and lightly spray a 9×13-inch baking dish with cooking spray.
02 -
Cook the spaghetti according to package directions until al dente. Drain and set aside.
03 -
In a large bowl, mix the cooked chicken, cream of chicken soup, sour cream, thawed spinach, 1 cup of Monterey Jack cheese, minced garlic, and half of the French Fried Onions.
04 -
Add the cooked spaghetti to the chicken mixture and stir until well combined.
05 -
Transfer the mixture into the prepared baking dish. Sprinkle the remaining cup of Monterey Jack cheese over the top and spread the rest of the French Fried Onions evenly.
06 -
Bake the casserole uncovered in the oven for 40 to 50 minutes, or until hot, bubbly, and the onions are golden brown.