Preheat the oven to 350°F. Butter a 9x13-inch baking dish and set aside.
In a large skillet set over medium-high heat, cook the bacon until evenly browned and crisp, about 8 minutes. Transfer to paper towels with a slotted spoon and let drain.
Meanwhile, bring a large pot of salted water to a boil. Add the cauliflower and cook until tender, 10–15 minutes. Drain well. In a bowl, mix sour cream, Cheezy Ranch dressing and ranch seasoning mix until well combined. Pour mixture over cauliflower and stir to coat.
Place cauliflower into the baking dish and cover with foil. Bake for 20–25 minutes; then uncover, top with Cheez-Its®, bacon and cheese, and continue to cook until the cheese is melted and bubbling, about 8–10 minutes.
Garnish with scallions and serve immediately.