Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain.
In a large saucepan or deep skillet, melt the butter over low to medium heat; blend in flour. Slowly add turkey stock, pasta sauce, and water. Mix well. Stir in onion soup mix and garlic; season with salt and pepper.
Sprinkle in the Monterey Jack, Cheddar cheese and turkey. Stir until the cheese is melted and the meat is heated through. Spoon sauce over pasta and serve.