HEAT grill to medium-high heat. Reserve 2 Tbsp. dressing. Thread shrimp and onions alternately onto 4 skewers; thread lemon wedges onto ends. Brush with remaining dressing.
GRILL 6 to 8 min. or until shrimp turn pink, turning occasionally. Meanwhile, mix reserved dressing with olives and tomatoes.
SERVE kabobs topped with olive mixture.