Combine the Greek Seasoning and paprika with the oils and vinegar in a medum-sized bowl (one that will hold everything). Add the mushrooms and marinate for several hours. Add the onion, tomatoes, avocado, celery, and parsley
. Chill for 1 hour before serving. At serving time, add the olives. Serve in bowls lined with lettuce leaves. This is as good, if not better, the next day. The dregs are a great dressing for a tossed salad. Serves 4.