Preheat the grill or grill pan over medium heat.
Cut the heads of romaine lettuce in half lengthwise, keeping the core intact.
In a small bowl, mix the olive oil, garlic powder, salt, and black pepper until well combined.
Brush the cut sides of the romaine with the olive oil mixture.
Place the romaine halves cut-side down on the grill and cook for 2-3 minutes or until grill marks appear and the leaves are slightly wilted.
Carefully flip the romaine halves and grill for another 1-2 minutes.
Remove from the grill and place on a serving plate.
Drizzle the balsamic vinaigrette over the grilled romaine and sprinkle with grated Parmesan cheese.
Optionally, add cherry tomatoes for garnish.
Serve immediately and enjoy!