To make filling, combine turkey, rice, onion, peas, feta, tomato paste, garlic and thyme in a large bowl.
Spoon filling evenly into bell peppers. Preheat oven to 350 degrees. Transfer peppers to a 9 inch square baking dish. Pour tomato puree over peppers; add eough water so that liquid comes one fourth up sides of peppers. Cover with foil and bake, basting occasionally with juices, 35 minutes. Uncover and bake until peppers are tender and until instant-read thermometer inserted into filling registers 165 degrees, 20-25 minutes. Let peppers stand 5 minutes before serving.
**To Freeze** Transfer uncooked stuffed peppers top side up to a 5 1/4-6 c freezer container. Cover and freeze up to 1 month. To serve, thaw peppers in refrigerator overnight. Follow cooking directions above.