Place potatoes and water in a 3-qt. microwave-safe bowl. Cover; microwave on high for 4-5 minutes or until potatoes are crisp-tender. Add the onion; cover and cook for 1-2 minutes or until onions are tender. Stir in the coleslaw mix. Cover and cook for 2-3 minutes longer or until potatoes are tender; drain.
In a large skillet, saute corned beef in oil for 3-4 minutes; drain. Stir in the remaining ingredients. Cook and stir for 1 minute or until heated through. Add to the potato mixture; toss to combine. Cover and microwave for 1-2 minutes or until heated through. Yield: 4 servings.