Savory Grilled Potatoes

In a large bowl, combine the first 7 ingredients. Add potatoes and onion; toss gently to coat. Spoon onto a double thickness of greased heavy-duty foil (about 18 in. square). Dot with butter. Fold foil around potato mixture and seal tightly. Grill, covered, over medium heat until potatoes are tender, turning once, 30-35 minutes.