Mix together salt, pepper, chili powder, paprika, garlic powder, dried oregano, and red pepper flakes in a small bowl. Put sliced peppers and onions into a large mixing bowl and cover with half of the seasoning mix, applying as evenly as you can.
Slice chicken breasts into thin strips and place into a separate mixing bowl. Add the remaining seasoning mix and apply evenly to the raw chicken strips.
Put 1 tbs of oil into either a wok or a deep skillet. Heat on medium-high heat for about 2 minutes. Add the peppers and onions to the pan and cook, stirring frequently until they are tender (approximately 5 minutes). Remove from the pan and place back into the large mixing bowl.
Add the remaining 1 tbs of oil to the pan and add the sliced chicken. Stir-fry the chicken until fully cooked, for about 5 minutes. Add the cooked vegetables back to the pan and continue cooking for another 2 minutes, stirring often.