Preheat your oven to 425°F (220°C).
In a mixing bowl, combine the olive oil, chili powder, cumin, garlic powder, smoked paprika, salt, and black pepper. Whisk until well combined.
Cut the chicken breasts into thin strips and add them to the bowl with the spice mixture. Toss to coat the chicken evenly.
On the large baking sheet, spread the sliced bell peppers and onions evenly. Place the seasoned chicken strips on top of the vegetables.
Bake in the preheated oven for about 25 minutes, or until the chicken is cooked through and the vegetables are tender.
Remove from the oven and let it cool for a few minutes. Toss everything together on the baking sheet.
Warm the tortillas in a dry skillet or microwave. Serve the chicken and veggie mixture on tortillas with lime wedges, and your choice of toppings.
For added flavor, consider marinating the chicken in the spice mixture for 30 minutes before roasting.
Feel free to substitute your favorite vegetables, such as zucchini or mushrooms, to customize your fajitas.
Leftovers can be stored in an airtight container in the refrigerator for up to 3 days. Reheat in the oven or microwave before serving.