Combine first 6 ingredients in a small bowl. Whisk until well blended. Cover, and set aside.
Combine romaine lettuce and iceberg lettuce in a large bowl. Place 2 cups lettuce mixture in each of 4 large salad bowls. Arrange 2 ounces chopped turkey, 1/4 cup cheese, 1/4 cup corn, 1/4 cup red bell pepper, 2 tablespoons celery, and 2 tablespoons onion over each. Serve vinaigrette with salad.