In 2 1/2 quart microwave-safe casserole dish** combine Simply Potatoes and water.*** Cover; microwave on HIGH 10 to 12 minutes or until Simply Potatoes are tender. Drain water.
Meanwhile in large bowl whisk together mayonnaise, mustard, vinegar, salt and pepper until smooth. Add cooked potatoes, celery, red pepper and chopped eggs. Stir gently. Refrigerate 1 hour to blend flavors.