Preheat the oven to 350F. Spray a 9 x 11 or similar-sized casserole dish with nonstick cooking spray.
In a large mixing bowl, combine the uncooked macaroni, cooked turkey, cream of mushroom soup, chicken broth, frozen peas and carrots, diced onion, shredded cheese, salt, and pepper.
Stir everything together until evenly combined. Make sure the pasta is well coated with liquid so it cooks properly.
Pour the mixture into the prepared casserole dish and spread it out evenly.
Cover tightly with foil and bake for 30 minutes.
Remove the foil and continue baking for an additional 15 to 20 minutes, or until the pasta is tender and the casserole is bubbly.
Let the casserole rest for 5 to 10 minutes before serving so it sets up slightly.
Notes
If using egg noodles instead of macaroni, check for doneness a few minutes early as they cook faster.For a creamier casserole, add an extra ¼ cup chicken broth before baking.Cream of chicken soup can be substituted for cream of mushroom.This casserole can be assembled up to 24 hours in advance and baked when ready. Add 10 extra minutes to the covered bake time if baking straight from the refrigerator.