* Finely chop the scallions or green onions including a few green tops. ** Oranges should be pared and sectioned, or can be unpared, cut into wedges. *** Avocados should be pared and cut into wedges. Sprinkle the scallions with the lime juice and 1/4 t salt; cover and refrigerate. Mix the remaining ingredients except the lettuce, oranges and avocados and refrigerate at least 1 hour. Spoon chicken mixture onto lettuce. Garnish with oranges and avocados; sprinkle with scallions.