Whisk orange juice, vinegar, molasses, orange peel, and all but 1 teaspoon garlic in medium saucepan. Bring to boil over medium-high heat. Reduce heat to medium and simmer until reduced to 2 cups, about 10 minutes. Stir in pepper sauce. Cool marinade to room temperature.
Place chicken in 11x7x2-inch glass baking dish. Pour marinade over. Refrigerate at least 4 hours and up to 1 day.
Prepare barbecue (medium-high heat). Remove chicken from marinade, shaking off excess. Transfer marinade to saucepan. Stir in reserved 1 teaspoon garlic. Boil over medium-high heat until reduced to 11/4 cups, about 5 minutes. Transfer to serving bowl. Season chicken with salt and pepper. Grill until cooked through, about 5 minutes per side. Transfer chicken to cutting board; let stand 5 minutes. Cut chicken crosswise on diagonal into 1/2-inch-thick slices; transfer to plate. Serve, passing sauce separately.
