In a resealable plastic bag combine garlic, rosemary, oregano, kosher salt, black pepper and olive oil. Place the steak in the bag and massage bag to mix ingredients and distribute into the steak. Squeeze the excess air from the bag and seal. Marinate for at least 30 minutes at room temperature.
Preheat grill or grill pan to medium-high heat and lightly oil grate. Remove steak from the marinade, shake off excess and discard the remaining marinade. Cook the steak on the preheated grill to desired degree of doneness, about 4 minutes per side for medium-rare. Allow the steak to rest in a warm place for 5 minutes before slicing thinly across the grain.
While steak is grilling place grape clusters on hot grill; cook 4 to 5 minutes or until the grapes begin to char and soften, turning occasionally.
In a small bowl mash together the butter, blue cheese, chives, 1/8 teaspoon of black peppe and salt; set aside.
Serve rested steak with a dollop of blue cheese butter alongside grilled grapes.