Preheat the oven to 400°F (200°C).
In a large bowl, combine sliced chicken, bell peppers, and onion.
Drizzle olive oil over the mixture.
Add chili powder, cumin, garlic powder, salt, and pepper.
Toss everything until well coated.
Spread the mixture evenly on a sheet pan.
Bake in the preheated oven for 25 minutes.
Stir halfway through cooking for even roasting.
Remove from the oven and let it rest for 5 minutes.
Serve with warm tortillas and your favorite toppings.