Gather all ingredients.

Preheat the oven to 350 degrees F (175 degrees C).

Bring a large saucepan of water to a boil. Add cauliflower and cook until tender, but not overly soft, 3 to 5 minutes.

Drain well and transfer cauliflower to a large bowl. Use a potato masher to mash cauliflower, leaving some chunks.

Reserve 1/2 cup Cheddar cheese and 1 tablespoon bacon bits. Mix remaining 1 cup Cheddar cheese, remaining bacon bits, cream cheese, sour cream, green onions, butter, salt, and pepper into mashed cauliflower in the bowl.

Transfer mixture to an 8-inch square baking dish. Sprinkle reserved Cheddar cheese and bacon bits on top. Bake in the preheated oven until hot and bubbly, 30 to 35 minutes.