In a small bowl, combine chili powder, ground cumin, smoked paprika, garlic powder, onion powder, dried oregano, salt, and black pepper to make the fajita seasoning.
Place the sliced chicken breast in a large bowl and sprinkle half of the fajita seasoning over it. Toss to coat evenly.
Heat olive oil in a large skillet over medium-high heat.
Add the seasoned chicken to the skillet and cook for 5-7 minutes, stirring occasionally, until the chicken is cooked through and lightly browned.
Remove the chicken from the skillet and set aside.
Add the sliced bell peppers and onion to the same skillet. Sprinkle the remaining fajita seasoning over the vegetables and sauté for 5-7 minutes until they are tender-crisp.
Return the cooked chicken to the skillet with the vegetables and stir to combine. Cook for an additional 1-2 minutes to heat through.
Warm the whole wheat tortillas in a dry skillet or microwave for about 20 seconds until pliable.
Divide the chicken and vegetable mixture evenly among the tortillas.
Garnish with chopped fresh cilantro and serve with lime wedges on the side for squeezing over the fajitas.