Soak 16 wooden skewers in water for 10 to 20 minutes.
Thread each skewer with 2 pieces chicken, 1 tomato, 1 onion wedge, 2 pieces of zucchini, 1 piece of yellow squash, and 1 piece of pepper, alternating vegetables and chicken.
Brush vegetables and chicken with olive oil and place on grill.
Cook 5-6 minutes; turn over and cook another 6-7 minutes until chicken is cooked through.