1 small head cauliflower, broken into flowerets
1 lb. broccoli, broken into flowerets
1/2 lb. fresh mushrooms, sliced
1 small purple onion, sliced, separated into rings
2 stalks celery, sliced or diced
1 cup vegetable oil
1/2 cup white wine vinegar
1/2 cup sugar
1 tbsp. Italian seasoning
2 tsp. dry mustard
1 tsp. salt
Lettuce leaves (optional)

Combine first 5 ingredients in a large bowl; set aside. Combine oil and next 5 ingredients; stir well and pour over vegetables. Toss gently to coat; cover and chill 3 hours, stirring occasionally. Serve with a slotted spoon over lettuce, if desired.