Easy Casserole

1 Pound Lean ground beef
2 Medium Potatoes, peeled and diced
2 Tablespoon Onion, chopped
4 Ounce Can sliced mushrooms,drained
10 1/2 Ounce Can cream of mushroom soup
Salt and pepper, to taste
3 Ounce Can french fried onion rings

Place all ingredients except onion rings in a 3 quart casserole. Mix well. Cover. Microwave at high until potatoes are tender. 16 to 18 minutes. stirring twice during cooking time. Sprinkle onion rings on top. Microwave, uncovered at high 1 1/2 to 2 minutes.