For the vinaigrette: Whisk together the mustard, red wine vinegar and chopped oregano in a small bowl. Whisk in the olive oil until the consistency is smooth and creamy. Season with salt and pepper to taste. Set aside.
For the salad: Toss together the radicchio, Belgian endive, arugula, grated Parmigiano-Reggiano cheese and pine nuts in a large salad bowl. Pour the vinaigrette over the salad ingredients and toss lightly to coat. Divide onto four chilled salad plates and serve.