Wash and dry lettuce, keeping the leaves whole. Line a platter or shallow bowl with the leaves. Combine the cucumber, tomato wedges, and bell pepper slices in a bowl and toss to mix. Combine the oregano, vinegar, and pepper and whisk to blend. Add to the vegetable mixture and toss to coat evenly. Arrange the vegetables on top of the lettuce leaves and sprinkle with the feta cheese.
Makes 6 servings