Preheat grill to medium-high heat. In a large bowl whisk together the olive oil and Sweet Mustard Moppin' Sauce. Add the potatoes and onions; toss to coat. Coat heavy-duty foil with nonstick spray. Place potatoes and onions on foil and seal. Set bowl aside. Grill approximately 20-25 minutes or until potatoes are fork-tender.
Transfer potatoes to reserved bowl; add Dijon mustard and salt and pepper to taste. Toss to combine. Makes 6 servings.
Tip: If using other potatoes, dice into 1-inch pieces to ensure even cooking.