Place chicken wings, buttermilk and ¼ cup buffalo sauce in a large resealable plastic bag. Place in dish or bowl and marinate in fridge for 2 to 8 hours. Drain wings and pat dry, then place in a clean plastic bag.
In a small bowl, stir together garlic powder, oregano, salt, pepper and cayenne pepper. Add to wings and toss to evenly coat. Let sit at room temperature for about 30 minutes.
Preheat gas grill to medium-high heat, about 450° F. Place wings on grill at least 2-inches apart, close lid and reduce heat to medium. Cook 5-8 minutes or until bottoms have sear marks. Rotate and cook 5-10 minutes longer, until internal temp reaches 165°. Remove from grill and lightly tent with foil.
Place 1-cup buffalo sauce, butter, worcestershire sauce and garlic in a small saucepan over medium heat. Cook 5 minutes or until butter is melted, stirring occasionally. In a large bowl, toss grilled wings and buffalo sauce to coat, then serve.