Grill sausage on barbecue preheated to medium-high, turning frequently about 15 min. or until cooked through and internal temperature reached 165°F (74°C). Meanwhile, thread grapes onto skewers and place on grill. Also lay onions directly on grill. Cook grapes and onions 3 to 5 min. or until lightly charred and tender. Remove grapes from skewers. Chop onions into bite-sized pieces. Thinly slice sausage. Set aside.
Grill pizza crust for 2 min. per side, or until lightly charred. Remove from grill. Sprinkle mozzarella on crust. Top with sausage, grapes and onion. Place pizza on indirect heat on grill. Cook, covered, 8 to 10 min. or until cheese is melted. Cut into wedges and serve with green salad.