Preheat oven to 350°. Sauté onion, red and green bell pepper, and celery in hot oil in a small skillet over medium-high heat 5 to 7 minutes or until vegetables are tender.
Stir together ground chicken, next 8 ingredients, and sautéed vegetables in a large bowl just until combined.
Place mixture in a lightly greased 9- x 5-inch baking dish. Bake at 350° for 1 hour to 1 hour and 10 minutes or until a meat thermometer registers 165°. Let stand 10 minutes before slicing. Serve meatloaf slices in pita rounds with desired toppings.
Note: For testing purposes only, we used Cavender's All Purpose Greek Seasoning.