Season chicken, if desired, with salt and pepper. In large nonstick skillet, melt 2 tablespoons Country Crock® Spread over medium-high heat and brown chicken. Remove chicken and set aside. In same skillet, melt remaining 2 tablespoons Spread over medium-high heat and cook onion, mushrooms, garlic, oregano, salt and pepper, stirring occasionally, until onion is tender, about 5 minutes. Stir in vinegar and cook 1 minute. Add tomatoes. Return chicken and any chicken juices to skillet and bring to a boil over high heat. Reduce heat to low and simmer uncovered until chicken is thoroughly cooked, about 5 minutes. Serve, if desired, with hot cooked rice or pasta.