Preheat the barbecue to medium-high. Brush the chicken with the oil; sprinkle and rub with the chili powder, cumin, oregano, salt and pepper. Place the chicken breasts on the grill bone-side down. Cook for 2 to 3 minutes, and then turn them skin-side down. Cook skin-side down for 2 minutes, or until the chicken achieves a nice colour but is not overly dark. Move the breasts to one side of the barbecue and turn them back to skin-side up. Turn the heat off under the chicken and leave the other side of the barbecue set to medium-high. Cover and cook for 20 minutes. Meanwhile, combine the barbecue sauce, orange juice, and peppers in a bowl. Once the chicken has cooked for 20 minutes, baste it with half the barbecue sauce mixture. Cover and cook 10 minutes more before basting with the remaining sauce. Cover and cook for 5 to 10 minutes more, or until cooked through.
Note: Chipotle peppers (smoked jalapenos) are sold in tins in the Mexican food aisle. Unused peppers can be stored in a tightly-sealed jar in the fridge for a few weeks.