Prepare grill to medium-high heat. Divide all vegetables, Vidalia® Onion Dressing and oil between 2 (1-gallon) freezer bags. Seal well; toss to coat. Let stand 10-15 mintues.
Remove vegetables from bags (reserve marinade). Place on grill. Grill, turning occasionally and basting with reserved marinade, until vegetables have grill marks and are crisp-tender, about 8-10 minutes. Let vegetables rest until room temperature; cut peppers into slices.
Meanwhile, in small bowl, combine mayonnaise, sour cream and Artichoke & Spinach Warm Dip Mix; mix until well combined. Thin with milk to desired consistency, if desired. Serve with grilled vegetables.
Makes 12 servings.
Make ahead: Prepare through step 3 up to 1 day ahead. Refrigerate grilled veggies and dip in separate containers. Serve veggies at room temperature.