Sprinkle chicken with salt and black pepper. Heat oil in a 12-inch nonstick skillet over medium-high heat. Add chicken; cook 2 minutes on each side or until lightly browned. Add onion and garlic; sauté 2 minutes or until onion is tender. Stir in wine, 3 tablespoons cilantro, and next 4 ingredients (through red pepper); bring to a boil. Cover, reduce heat, and simmer 30 minutes or until chicken is done.
Transfer chicken to a serving platter, and keep warm. Increase heat to medium-high; cook until sauce is reduced to 1 cup (about 5 minutes). Stir in grapes. Spoon sauce over chicken; sprinkle with remaining 3 tablespoons cilantro.