2/3 cup balsamic vinegar
1 tablespoon black pepper
2 cloves garlic
1/4 cup olive oil
Poke the meat with a fork to help the marinade penetrate. Mix the remaining ingredients in a large resealable bag. Drop the steak into the bag, seal, and refrigerate for 1 hour or up to 24 hours.
Preheat a grill to medium for direct heat. Remove the meat from the bag, reserving the marinade. Grill the meat for 6 to 8 minutes per side or until a thermometer inserted into the thickest part registers 145°F for medium rare. In a small saucepan, boil the reserved marinade for 5 minutes.
Slice the meat diagonally across the grain in thin slices and drizzle with the marinade. Divide evenly onto 4 plates.