1. Remove beef tips from bag and place in 8x8-inch microwave-safe glass dish.
2. Cover with plastic wrap and cook on HIGH 12-15 minutes.
3. Stir onions and mushrooms and corn into beef mixture.
4. Cover with wrap and microwave 4-6 minutes.
5. Spread potatoes over mixture.
6. Cover with wrap and microwave an additional 2-4 minutes.
Tip: Be very careful when removing plastic wrap. The steam can burn.