Rinse and pat dry chicken breasts. Season with salt and pepper. In a large saute pan, heat 2 tablespoons olive oil. Add the chicken and brown well on both sides, about 5 minutes. Remove chicken and set aside. Add remaining 1 tablespoon of olive oil to the pan and heat until hot but not smoking. Add the onion and squash and cook until just soft. Stir in the garlic and mushrooms. Cook until vegetables are crisp tender about 5 minutes. Stir in the red peppers and chopped tomatoes and cook until most of the liquid has evaporated. Using a slotted spoon, remove the vegetables to a bowl. To the same pan, add the marinara sauce, 1/2 cup of reserved tomato juices, tomato paste, and red wine vinegar. Bring to a boil and reduce the heat to medium low. Return the chicken breasts to the pan and cook until chicken is no longer pink, about 10 minutes. Just before chicken is done, return the vegetables with the freshly chopped herbs to the pan and heat through. Transfer chicken and vegetables to a serving platter.
courtesy of Gourmet Magazine