1 pkg. frozen green beans (9 oz.)
1 lg. onion, sliced into rings
1/4 c. grated Parmesan cheese
1 can mushrooms (2 1/2 oz.) drained and sliced
2 tbsp. butter

Cook green beans according to package directions. (Canned beans may be substituted.) Saute onions in butter until tender. Add mushrooms. Drain beans; stir in with onions. Add cheese. Serve warm with additional cheese, if desired. Serves 4-6.