Whisk together olive oil, balsamic vinegar, Dijon mustard, and minced garlic in a small bowl. Pour half of this mixture over the beef steak and let it marinate for 30 minutes.

Preheat a grill to medium-high heat. Remove the meat from the marinade and grill for 5 to 7 minutes per side for medium-rare. Let it rest for 10 minutes before slicing thinly against the grain.

In a large serving bowl, combine the romaine lettuce, cherry tomatoes, sliced red onion, and kalamata olives.

Top the greens with the sliced meat and sprinkle with blue cheese crumbles. Drizzle the remaining dressing over the top before serving.