Preheat oven to 350. Spray a baking sheet with cooking spray. Put the cauliflower quarters on the baking sheet and cook for 30 minutes.
Meanwhile, stir together the mayo and blue cheese.
After 30 minutes the cauliflower should be slightly tender. Spread with the blue cheese sauce. Sprinkle on the bacon. Bake for 10-15 minutes until the cheese sauce is golden.