Preheat oven to 350°F. Spray cookie sheet with cooking spray.
Place half of the tortilla chips on cookie sheet. Top with half of the cheese, dressing, onions and bacon. Repeat layers.
Bake 3 to 4 minutes or until cheese is melted. Remove from oven and let stand 2 to 3 minutes. Using a large spatula, carefully slide nachos onto large serving platter to serve.