For dressing, in a screw-top jar combine cranberry juice cocktail, oil, vinegar, sugar, and salt. Cover and shake well. Chill until serving time.
Meanwhile, rinse romaine and endive; pat dry. Line 3 very large or 4 large serving platters with some of the romaine and all of the endive. Coarsely shred remaining romaine; spread over platter. Arrange cucumbers, mushrooms, red peppers, and sprouts, if desired, on lettuce-lined platter. If desired, cover and chill for up to 24 hours.
To serve, halve, seed, peel, and thinly slice avocados, brushing slices with lemon juice. Add avocados to platter. Shake dressing well and serve with salad. Makes 20 servings.
For softer-looking red pepper strips, blanch the pepper strips in boiling water for 1 to 2 minutes. Drain well and chill thoroughly.
Combine dressing ingredients; cover and chill. Arrange vegetables (except avocados) on romaine- and endive-lined platter; cover and chill for up to 24 hours. Serve as directed above.