Stir together first 3 ingredients. Pour into a large heavy-duty zip-top plastic bag.
Add fish; seal and chill 3 hours. Drain. Thread fish and onion onto 12-inch skewers.
Grill in a grill basket, covered with grill lid, over high heat (350° to 400°) 8 minutes, turning a quarter turn every 2 minutes, basting with Indonesian Barbecue Sauce. Serve kebabs at room temperature or chilled. Serve with additional Indonesian Barbecue Sauce.