In large bowl, combine chicken, celery, red pepper, cilantro, scallions and watercress or arugula leaves. Toss well to combine.
Add ½ cup Sesame Ginger Vinaigrette (recipe follows) and salt and pepper; toss gently again.
Divide salad evenly among four plates or place on large serving platter.
Sesame Ginger Vinaigrette:
In medium bowl, stir together orange zest, orange juice, soy sauce, rice wine vinegar, honey, ginger, scallions and garlic. Slowly whisk in sesame and canola or safflower oil, just until incorporated. Season and salt and pepper.
Stir in sesame seeds just before serving. Dressing can be refrigerated in airtight container for up to one week.