1Between pieces of plastic wrap or waxed paper, place each chicken breast smooth side down; gently pound with flat side of meat mallet or rolling pin until about 1/4 inch thick.
2In shallow medium bowl or pie plate, mix bread crumbs, cheese, salt and pepper. Coat chicken with crumb mixture, pressing to coat well on both sides.
3In 12-inch nonstick skillet, heat 2 tablespoons of the oil over medium-high heat. Cook chicken in oil 6 to 10 minutes, turning once, until golden brown on outside and no longer pink in center. Remove chicken from skillet; cover to keep warm.
4To skillet, add remaining 1 tablespoon oil, 2 cups of the tomatoes, the onions and garlic; cook and stir 2 minutes. Stir in vinegar; cook 30 seconds longer. Remove from heat; stir in remaining 1 cup tomatoes and the oregano. Serve over chicken. Garnish with additional fresh oregano sprigs, if desired.