1. Preheat the oven to 350°F.
2. Place the bread slices in a bowl, sprinkle the olive oil over them, and toss. Spread the slices out in a single layer on a baking sheet, and bake until golden brown, about 20 minutes. Set them aside.
3. Separate the romaine lettuce leaves, discarding any tough or bruised leaves. Rinse the leaves under cold running water, drain them well, and pat them dry. Tear the leaves into pieces.
4. Place the romaine in a large salad bowl, and add the radicchio, cucumber, tomato, onion, feta, and parsley.
5. Prepare the dressing: Whisk the vinegar, mustard, and salt and pepper together in a small bowl. Whisking constantly, slowly drizzle in the olive oil; continue whisking until the dressing has thickened slightly.
6. Just before serving, season the salad with salt and pepper, and drizzle it lightly with the dressing. Sprinkle the lemon zest and juice over the salad, and toss. Toss in the croutons. Serve immediately.