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.
* To prepare hard boiled eggs, place eggs in 3 quart saucepan. Cover eggs with cold water. Bring water to a boil. Reduce heat to low. Simmer 15 minutes; drain water. Add cold water to saucepan. Let stand 5 minutes. Drain; peel and chop eggs.
** A 9-inch square baking dish can be used for a 2 1/2 quart casserole baking dish.
***Place 1 package Simply Potatoes Diced Potatoes with Onion in a medium saucepan with 1/2 cup water. Bring to a boil; reduce heat to medium-low and cover. Cook about 10 minutes or until potatoes are just tender.