In a large bowl, combine the flours, salt and, if desired, garlic powder. Stir in water and oil. Turn onto a floured surface; knead until smooth and elastic, 8-10 minutes. Cover and let rest for 30 minutes. Divide dough into 10 portions. On a lightly floured surface, roll each portion into a 6-in. circle. In a large cast-iron or other heavy skillet, cook breads over medium heat until lightly browned, 1 minute on each side. Keep warm.