Combine potatoes and onion in a large bowl. Combine lemon rind and next 8 ingredients. Pour lemon mixture over potato mixture; toss well to coat. Place potato and onion mixture in grilling bag, arranging potato mixture in a single layer. Pour any remaining lemon juice mixture over potato mixture.
Place grilling bag on grill rack over medium-hot coals (350° to 400°); cover and grill 15 minutes. Open bag and stir gently. Reseal bag, and grill an additional 15 minutes or until potatoes are tender.