Preheat your oven to 400°F (200°C).
In a large bowl, combine the sliced chicken, bell peppers, and onion.
Drizzle olive oil over the mixture.
Add chili powder, cumin, garlic powder, salt, and pepper.
Toss everything until evenly coated.
Spread the mixture evenly on a sheet pan.
Bake for 20-25 minutes, stirring halfway through.
Check that the chicken is cooked through (165°F or 75°C).
Remove from the oven and let it rest for a few minutes.
Serve in warm tortillas with your favorite toppings.