Greek Salad with Shrimp

1 pound large shrimp -- peeled and de-veined
1 teaspoon oregano
salt and pepper
1 (10oz) bag torn romaine
2 tomatoes -- cut in wedges
1 red onion -- thinly sliced
1/2 cup crumbled feta cheese
2 tablespoons lemon juice
2 tablespoons water
2 teaspoons Dijon mustard
1 teaspoon olive oil

Place shrimp in med. saucepan and add water to cover. Bring too a simmer over med. heat. Turn off heat and let stand 1 min. Drain and place in large bowl. Add oregano, salt and pepper. Toss to mix. (Can be done ahead of time and refrigerated.) Add lettuce, tomato, onions, and feta. Toss well. In a small bowl, whisk together lemon juice, water, and mustard. Whisk in oil. Pour over salad and toss well.