Fold an 18-in. square piece of heavy-duty foil in half to make an 18x9-in. strip. Place strip on bottom and up sides of a 5- or 6-qt. slow cooker. Coat strip with cooking spray., In a large bowl, combine the first 6 ingredients. Add turkey, 2 cups cheddar cheese and Parmesan cheese; mix lightly but thoroughly (mixture will be moist). Shape meat into an 8x5-in. loaf; place in center of strip., Cook, covered, on low 3-4 hours or until a thermometer reads 165°. Sprinkle with remaining 1/2 cup cheddar cheese during the last 20 minutes of cooking. Using ends of foil strip as handles, remove meat loaf to a platter. Let stand 15 minutes. , Freeze option: Prepare meat loaf as directed, omitting cheddar cheese over top. Securely wrap cooled meat loaf in foil, then freeze; freeze remaining 1/2 cup cheddar cheese in a freezer container. To use, partially thaw in refrigerator overnight. Unwrap meat loaf; reheat on a greased 15x10x1-in. baking pan in a preheated 350° oven until heated through and a thermometer inserted in center reads 165°. Sprinkle with cheese.