Find recipes for Low-Fat Ranch Dressing and other Course recipes. Get all the best recipes at . Recipe directions: In a bowl, combine oil, vinegar, sweetener and marjoram. Whisk in buttermilk, yogurt and mayonnaise. Stir in onion, parsley and garlic. Cover and refrigerate for 6 hours or overnight to thicken. whisk before serving. serve over salad greens and vegetables of your choice. Refrigerate leftover dressing.