Line a rimmed baking sheet with foil and set a wire rack on top.
Spray rack with cooking spray.
In a large bowl, whisk buttermilk with egg white, add chicken and turn to evenly coat.
Measure flour, salt, garlic powder, oregano, chili powder and baking powder into a large plastic bag.
Close top and gently shake to evenly mix.
Remove chicken, one piece at a time, from buttermilk and shake off excess liquid, then place in bag.
Close top and shake gently to evenly coat.
Remove from bag, shaking off excess coating, then place on rack, repeat with remaining chicken, one piece at a time.
Discard any remaining milk and flour mixtures.
Using a brush, lightly dab oil as evenly as possible over coating on chicken.
Bake in centre of preheated oven until coating is crisp and golden, about 30 minutes.
If you have time, let chicken marinate in buttermilk before roasting. This makes it even more tender and adds tang, too! Place chicken and buttermilk mixture in a large plastic bag. Push chicken down into marinade, then squeeze out as much air as possible from bag. Seal tightly with an elastic band as close to chicken as possible. Place in a large bowl. Refrigerate 4 hours or overnight. Then proceed with recipe as written.