1 lb. mushrooms, sliced
1 med. size purple onion, thinly sliced & separated into rings
1/2 c. finely chopped celery
1 c. tarragon wine vinegar
1/2 c. olive oil
1/2 c. vegetable oil
1 tsp. dried whole oregano
1 tsp. dried whole basil
1 tsp. dry mustard
1/8 tsp. salt
1/8 tsp. pepper
Lettuce leaves

Combine first 3 ingredients in a bowl. Combine vinegar and next 7 ingredients in a jar; cover tightly and shake vigorously. Pour over vegetables, stirring well. Cover and refrigerate 8 hours. To serve, drain mushrooms and place on lettuce leaves. 6 to 8 servings.