Combine orange juice, brown sugar, BBQ sauce, and chipotle peppers in a large ziptop bag.
Use a meat mallet or heavy rolling pin to flatten chicken breasts into even thickness.
Place chicken in bag with marinade. Refrigerate for 2 to 24 hours.
Remove chicken from fridge and let it sit at room temperature while you heat the grill. Heat grill to medium-high.
Remove chicken from marinade and season lightly with salt and pepper. Drizzle with olive oil. (Discard the marinade.)Grill chicken for 5 to 6 minutes per side, or until cooked through.
If desired, baste chicken with bottled bbq sauce the last minute of grilling.
