Preheat a grill. (If you don’t have a grill, you also can use a stovetop grill pan; in that case, skip this step.)
Wash and dry the romaine. If using romaine heads, remove a few of the outer-most leaves and save for a salad at another time.
Cut each romaine heart in half lengthwise. Drizzle each side liberally with olive oil and balsamic vinegar, and add several pinches kosher salt and fresh ground black pepper.
Place the romaine hearts on the grill, and grill for about 3 minutes on each side, until slightly charred.
Top with grated Parmesan cheese (or Easy Caesar Dressing) and serve immediately.