Prepare the Rosemary Mustard Sauce by combining mustard, brown sugar, Worcestershire sauce, rosemary, onion flakes garlic and pepper into a saucepan and cook over medium heat.
Whisk until sugar is melted and all ingredients are combined.
Set aside or refrigerate until ready to use.
Build a grill fire to about 350° with pecan or hickory.
Pat wings dry with paper towels and place on a clean baking sheet.
Cook wings over indirect fire with the grill closed for about 20 minutes.
Check internal temperature with a digital thermometer, cooking to about 160°.
Pour 1 cup of rosemary mustard sauce into a large bowl.
Add chicken wings to the bowl and toss with mustard until well coated.
Return mustard coated wings to the grill and cook for about 10 more minutes or until internal temperature reaches 165°.
Remove from grill and serve immediately.