Remove the stem from the head of iceberg lettuce. Cut the lettuce head into four equal wedges. Lay each wedge on its "back" on the plate, so the light-colored center of the lettuce points up.
Cook the bacon until crispy in a large skillet over medium heat, flipping as needed. Transfer to a paper towel-lined plate to drain. Crumble once cool enough to handle.
Drizzle 3 tablespoons of creamy blue cheese dressing on top of each lettuce wedge. (If you do this first, it helps the toppings stick.)
Top each wedge salad with tomato, red onion, crumbled bacon, and blue cheese crumbles. Serve immediately.