Prepare the baking dish

• Preheat oven to 350°F. Grease a 9x13-inch baking dish with butter or nonstick cooking spray.

Cook the pasta

• Bring a large pot of salted water to a boil. Cook the pasta according to package directions until al dente.
• Before draining, reserve ½ cup of the pasta water. Drain the remaining water.

Mix the casserole

Add the cooked pasta to the prepared baking dish.

Stir in:

• Rotisserie chicken
• Cream of chicken soup
• Greek yogurt
• Reserved pasta water
• Thawed and well-drained spinach

Mix until everything is evenly coated.

• Season lightly with salt and pepper if desired.

Add the toppings

• Sprinkle the shredded Monterey Jack cheese evenly over the casserole.
• Top with an even layer of French's Fried Onions.

Bake

• Bake uncovered for 30–35 minutes, or until hot, bubbly, and the cheese is melted.
• For extra crispy onions, loosely cover with foil for the first 20 minutes, then remove the foil for the last 10–15 minutes.

Rest and serve

• Let the casserole rest for 5–10 minutes before serving.