Preheat the air fryer to 375°F (190°C) for 5 minutes.
In a small bowl, combine the garlic powder, smoked paprika, dried oregano, salt, and black pepper.
Pat the chicken breasts dry with paper towels. Rub 1 tablespoon of olive oil evenly over the chicken breasts.
Sprinkle half of the seasoning mixture evenly over both sides of the chicken breasts.
In a separate bowl, toss the sliced red, yellow, and green bell peppers with the remaining 1 tablespoon of olive oil and the remaining seasoning mixture.
Place the seasoned chicken breasts in the air fryer basket in a single layer.
Arrange the seasoned bell peppers around the chicken breasts in the air fryer basket.
Cook for 9 minutes, then carefully flip the chicken breasts and stir the peppers.
Continue cooking for an additional 9 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the peppers are tender.
Remove the chicken and peppers from the air fryer and let the chicken rest for 3 minutes before slicing.
Serve the sliced chicken breasts alongside the cooked bell peppers.