Broccoli and Cauliflower Salad

1½ pounds fresh broccoli
1 medium cauliflower, cut into flowerets
1 red onion, thinly sliced
½ cup sliced celery
1 (2-ounce) jar chopped pimiento, drained
1 cup mayonnaise
2 Tablespoons sugar
1 teaspoon dry mustard
¼ teaspoon salt
¼ teaspoon freshly ground pepper
2 Tablespoons vegetable oil
Lettuce leaves

Remove broccoli leaves and cut off tough ends of stalks; discard. Wash thoroughly and cut into 1-inch pieces. Combine broccoli, cauliflower and next 3 ingredients in a large bowl. Combine mayonnaise and next 5 ingredients; spoon over vegetables, tossing to coat. Cover and chill. Serve salad with a slotted spoon on lettuce-lined plates. Yield 8 to 10 servings.