Fall greens with walnuts feta and walnut vinaigrette

2 heads radicchio, washed, dried and separated into leaves
2 large Belgian endives, washed, root end cut off separated into leaves
1 bunch watercress, stems trimmed, washed and dried
3 ounces feta cheese, crumbled
1/2 cup walnut halves, lightly toasted

For dressing:
1 tespoon Dijon mustard
2 tablespoons red wine vinegar
salt and pepper to taste
1/4 cup walnut oil
1/4 cup extra virgin olive oil