Toss beans with oil, salt and 1/8 teaspoon pepper in a bowl.
Transfer to a grill basket
Grill the beans, stirring occasionally, until tender-crisp and brown in spots, 8 to 10 minutes. If they're browning too much before they are tender, reduce the heat or move the grill basket to a cooler spot.
Combine duck butter, ketchup and the remaining 1/8 teaspoon pepper in a medium bowl.