3 tablespoons olive oil
2 small skinless boneless chicken breast halves

1 cup diced onion
1 large zucchini, halved lengthwise, seeded, cut into 1/2-inch cubes
1/2 large yellow crookneck squash, halved lengthwise, seeded, cut into 1/2-inch cubes
2 cups (packed) shredded mozzarella cheese (about 8 ounces)
1/3 cup plus 3 tablespoons chopped fresh cilantro

1 10-ounce purchased fully baked thin pizza crust (such as Boboli)
6 tablespoons purchased barbecue sauce