These marinated mushrooms can be served as an entrée or as a side dish.

In a skillet, heat oil and cook onions over medium heat until transparent.
Add mushrooms and cook until lightly brown.
Add remaining ingredients and cook 3 Minutes over medium heat stirring a few times.

Cool at room temperature. At this point the mushrooms can be refrigerated for up to 3 days. Take them out of the refrigerator 30 minutes before serving.
Just before serving put a leave of lettuce dessert plates and put marinated mushrooms on lettuce.