1. Preheat grill to 350° to 400° (medium-high) heat. Combine 1/4 cup orange juice, 3 Tbsp. soy sauce, 3 Tbsp. brown sugar, and next 5 ingredients in a shallow dish or large zip-top plastic freezer bag; add chicken. Cover or seal, and chill 10 minutes. Remove chicken from marinade, discarding marinade.
2. Grill chicken, covered with grill lid, 10 to 12 minutes on each side or until done. Remove from grill; cover with aluminum foil, and let stand 10 minutes.
3. Meanwhile, whisk together 2 tsp. brown sugar, remaining 3/4 cup orange juice, and 2 Tbsp. soy sauce in a small saucepan. Whisk together cornstarch and 2 tsp. water, and whisk into orange juice mixture. Bring mixture to a boil over medium heat, and cook, whisking constantly, 1 minute or until thickened. Brush sauce over chicken.