Preheat oven to 400 degrees F. Coat a large rimmed baking sheet with cooking spray.
Cut chicken breasts in half horizontally, then slice crosswise into strips. Combine oil, garlic powder and salt in a large bowl. Add the chicken and stir to coat with the spice mixture. Add bell peppers and onion and stir to combine. Transfer the chicken and vegetables to the prepared baking sheet and spread in an even layer.
Roast on the middle rack for 15 minutes. Leave the pan there and turn the broiler to high. Broil until the chicken is cooked through and the vegetables are browning in spots, about 5 minutes more. Remove from oven. Stir in lime juice.
Serve the chicken and vegetables in warmed tortillas.