In a small bowl, whisk the first nine ingredients. Place the chicken in a large resealable plastic bag; add 6 tablespoons vinaigrette. Seal bag and turn to coat; refrigerate for 2 hours. Cover and refrigerate remaining vinaigrette until serving.
Drain and discard marinade. Grill chicken, uncovered, over medium-low heat for 6-8 minutes on each side or until a meat thermometer reads 170°. Cut into strips.
In a large bowl, combine the romaine, bacon, tomato, mushrooms, walnuts, chicken and reserved vinaigrette; toss to coat. Yield: 4 servings.