1Place chicken in shallow glass or plastic dish or large resealable food-storage plastic bag. In small bowl, mix all marinade ingredients. Pour marinade over chicken; turn to coat chicken with marinade. Cover dish or seal bag; refrigerate, turning chicken occasionally, 8 hours or overnight.
2Heat gas or charcoal grill. In 2-quart saucepan, heat oil over medium-high heat. Cook onion and garlic in oil, stirring occasionally, until soft. Add 2 cups orange juice and the vinegar; heat to boiling. Reduce heat; simmer uncovered until mixture is reduced to 1 cup. Remove from heat; stir in brown sugar, ketchup and molasses. Stir in desired amount of chiles. Set aside.
3Remove chicken from marinade; discard marinade. Place chicken on grill over medium heat. Cover grill; cook 15 to 20 minutes, turning once or twice and brushing with glaze during last 2 minutes of grilling, until juice of chicken is clear when center of thickest part is cut (at least 165°F).
4Heat any remaining glaze to boiling; boil and stir 1 minute. Serve with chicken.