Arrange first 4 ingredients in an 11-x 7-inch baking dish; pour 1 cup Lemon-Garlic Greek Dressing over ingredients. Cover and chill 2 hours.
Place lettuce in a large salad bowl; top with chicken mixture. Sprinkle evenly with pepperoncini peppers, onion, and feta. Serve with remaining 1 1/4 cups Lemon-Garlic Greek Dressing.