Grilled Romaine with Blue Cheese-Bacon Vinaigrette

Our neighbor gave us this recipe.  Neither she nor I know the resource, so I'm not sure who to credit.  No matter, it is worth repeating!

Ingredients:
4 Tbls olive oil
3/4 cup finely diced red onion
1/2 Lb bacon, 1/4 inch diced
1/2 cup balsamic vinegar
3 heads romaine lettuce, cut in half lengthwise
1/2 cup crumbled blue cheese
Freshly cracked black pepper

Directions:
- Preheat a grill

- Heat 1 Tbsp olive oil in a large skillet over high heat.  Add the onion and bacon and cook until the bacon is crispy.  Remove the onion and bacon from the pan.  Add the balsamic vinegar and 1 Tbsp olive oil to the skillet and reduce for 2-3 minutes.  Remove from the heat and set aside.

- Brush the romaine with the remaining 2 Tbsp olive oil.  Place on the grill cut-side down and quickly sear until grill marks are visible.  Set aside.

- For each serving, place a half head of romaine cut-side up on a plate and drizzle the balsamic dressing on top.  Sprinkle with blue cheese and the bacon and onion, and garnish with cracked black pepper.