Meanwhile, in a large serving bowl, combine the red onion with the lemon juice, oregano, capers and garlic and let stand for 5 minutes. Whisk in the olive oil and then add the cucumber and olives. Fluff the bulgur with a fork and add it to the dressing. Add the lettuce, season with salt and pepper and toss well. Top the bulgur salad with the crumbled feta and serve right away.