Drain the artichoke hearts, reserving 1 tablespoon marinade. Set aside 12 artichoke-heart quarters, reserving the remaining quarters for another use. Combine the reserved marinade, lemon juice, and pepper; stir well with a wire whisk. Set dressing aside.
Spoon 1/2 cup fennel on each of 6 lettuce-lined salad plates. Fan the onion wedges, and place 1 wedge on each plate. Arrange 2 artichoke-heart quarters, 2 olives, and 2 orange slices around fennel. Drizzle dressing evenly over salads.