1. Cook bacon in a large nonstick skillet over medium heat until crisp.
2. Remove with a slotted spoon to a paper towel then set aside.
3. In same skillet cook onion in bacon drippings 1 minute over medium heat.
4. Add mushrooms then raise the heat to medium high and cook and stir 4 minutes.
5. Add spinach then cook and stir just until it is wilted about 1 minute.
6. Sprinkle with reserved bacon and ground pepper.