Stir together 1/2 cup mayonnaise and next 4 ingredients in a large bowl.
Add chopped chicken and grapes, tossing gently to coat.
Cover and chill at least 1 hour.
Stir in nuts just before serving.
Serve in stemware lined with lettuce leaves, if desired.
Serve this fruity, nutty chicken salad with assorted crackers and grapes for a filling lunch or a delicious brunch.