Preparation Score top of chicken breasts with sharp knife; place in large glass baking dish. Whisk 1/2 cup oil, lemon juice, 6 teaspoons oregano, and garlic in small bowl to blend. Season dressing to taste with salt and pepper. Chill 3 tablespoons dressing for tomatoes. Pour remaining dressing over chicken; turn chicken to coat. Cover; refrigerate at least 3 hours and up to 6 hours, turning occasionally. Toss olives, tomatoes, feta, remaining 2 teaspoons oregano, and reserved dressing in medium bowl. Heat remaining 2 tablespoons olive oil in heavy large skillet over medium-high heat. Add chicken and sauté until cooked through, about 3 minutes per side. Transfer to platter; season to taste with salt and pepper. Spoon tomato mixture onto chicken.
Preparation Score top of chicken breasts with sharp knife; place in large glass baking dish. Whisk 1/2 cup oil, lemon juice, 6 teaspoons oregano, and garlic in small bowl to blend. Season dressing to taste with salt and pepper. Chill 3 tablespoons dressing for tomatoes. Pour remaining dressing over chicken; turn chicken to coat. Cover; refrigerate at least 3 hours and up to 6 hours, turning occasionally. Toss olives, tomatoes, feta, remaining 2 teaspoons oregano, and reserved dressing in medium bowl. Heat remaining 2 tablespoons olive oil in heavy large skillet over medium-high heat. Add chicken and sauté until cooked through, about 3 minutes per side. Transfer to platter; season to taste with salt and pepper. Spoon tomato mixture onto chicken.