To prepare chicken, combine first 4 ingredients in a large zip-top plastic bag. Add chicken to bag; seal. Marinate in refrigerator 15 minutes, turning the bag occasionally.
Remove chicken from bag; discard marinade. Sprinkle chicken evenly with 1/2 teaspoon salt and 1/4 teaspoon pepper. Place chicken on grill rack coated with cooking spray; grill 5 minutes on each side or until done.
Preheat oven to 425°.
To prepare tomatoes, combine tomatoes and 2 teaspoons oil in an 8-inch square baking dish; toss gently. Bake at 425° for 18 minutes or until tomatoes are tender. Combine tomato mixture, parsley, and remaining ingredients, stirring gently. Serve with chicken.
Wine note: Chicken on its own is a flexible partner for wine, but the capers, lemon, and parsley in this dish call for a varietal that can handle the briny, tart, and herbal qualities of these ingredients: sauvignon blanc. Try Dry Creek Vineyard Fume Blanc 2006 from Sonoma County, California ($14.50). —Karen MacNeil