To prepare loaves, combine first 8 ingredients, stirring well. Divide mixture in half, forming each half into a 6 x 3-inch loaf. Place each loaf on a broiler pan coated with cooking spray; broil 7 minutes on each side or until done.
Sprinkle loaves with red pepper. Cut each loaf crosswise into 1/8-inch slices.
To prepare sauce, place cucumber and onion onto several layers of heavy-duty paper towels. Cover with additional paper towels; let stand 5 minutes.
Combine cucumber mixture, mint, and next 5 ingredients (mint through yogurt), stirring well. Divide meat slices evenly among pitas; top each serving with about 1/4 cup sauce.