Place the chicken breasts in a plastic freezer bag or casserole dish. Combine the remaining ingredients and pour over the chicken. Marinate for several hours, or overnight.
When ready to cook, line half of your grill with heavy aluminum foil. Preheat your grill to medium-high heat. Spray both sides with cooking spray. Combine all of the chopped vegetables, along with the garlic in a bowl or plastic bag and add the olive oil and herbs; season with salt and pepper.
Spread the vegetables on the foil-lined side of the grill, and cook the chicken on the other side. Stir the vegetables once or twice during the cooking process, and cook until tender, about 20 minutes. Cook until the chicken is done throughout and vegetables are tender. Serve immediately.