PREHEAT oven to 375ºF. Combine tomatoes, corn, onions and 1/4 cup of the dressing. Pour evenly into two 15x10x1-inch baking pans; spread evenly to cover bottoms of pans. Pour remaining 1/4 cup dressing over chicken in large bowl; toss to coat. Top tomato mixture in each pan with 5 of the chicken breasts.
BAKE 45 min. or until chicken is cooked through (165ºF).
TRANSFER chicken to serving platter; cover to keep warm. Mix both tomato mixtures in medium bowl. Add cheese and cilantro; stir until well blended. Serve with the chicken.