1. Mix together hash browns, cauliflower, 1 cup cheese, onion and bell pepper in a large mixing bowl.
2. In a separate bowl whisk together 1½ cups dressing and sour cream.
3. Pour over potato mixture; mix well.
4. Transfer potato mixture to a 2-quart baking dish.
5. Mix together remaining 1 cup cheese, ¼ cup dressing and bread crumbs. Sprinkle on top of casserole.
6. Bake at 350°F for 60 minutes, until browned, bubbly and cauliflower is tender.
7. Let stand for 10 minutes before serving.