This Beef and Mushroom Cauliflower Casserole is my cozy-night comfort food that just so happens to be low in carbs but rich in flavor.
It’s loaded with savory beef, earthy mushrooms, and creamy cauliflower rice—all wrapped up in a luscious cheese sauce that bubbles to golden perfection.
Why You’ll Love This Recipe
Low-carb and satisfying – Cauliflower rice keeps it light yet filling.
Ultra-creamy – The cheese and sour cream sauce is pure comfort.
Meal prep magic – Keeps well for days and reheats beautifully.
Veggie-packed – Mushrooms and cauliflower add nutrients and texture.
One-dish wonder – A complete meal baked in one casserole dish.
What You’ll Need (Ingredient Highlights)
Ground beef – Rich and savory base for this cozy casserole.
Mushrooms – Cremini mushrooms add earthy depth and hearty bite.
Cauliflower rice – Soaks up the flavors and keeps it low-carb.
Sour cream and mayo – The secret to that creamy, tangy sauce.
Mozzarella and Parmesan – Melty, golden, and full of flavor.
Steak seasoning – Adds the perfect savory blend to tie it all together.
Pro Tips Before You Start
Dry mushrooms well – Excess water will dilute the casserole.
Use fresh or frozen cauliflower rice – Either works, just cook off extra moisture.
Reduce the stock – Adds richness and keeps the sauce from getting watery.
Brown the meat fully – Adds flavor and helps it hold together.
Mix gently – Combine everything carefully so the texture stays fluffy, not mushy.
How to Make Beef and Mushroom Cauliflower Casserole
Step 1: Prep the Oven and Dish
Preheat your oven to 375°F (190°C).
Lightly grease a 13″x10″ baking dish with olive oil or non-stick spray.
Step 2: Make the Reduced Beef Stock
Simmer beef bouillon with water in a small pan until reduced to 1 tablespoon. Let cool.
Step 3: Brown the Ground Beef
In a large skillet, heat olive oil over medium-high heat.
Cook ground beef until fully browned, breaking it up as it cooks.
Transfer to the casserole dish.
Step 4: Cook the Mushrooms
Quarter the mushrooms. In the same skillet, heat another oil.
Sauté mushrooms over medium-high heat until browned and all liquid evaporates.
Add to the dish.
Step 5: Sauté the Onion and Cauliflower Rice
Add a bit more oil if needed. Sauté chopped onion until softened and lightly browned.
Add cauliflower rice, steak seasoning, salt, and pepper.
Cook on high for about 3 minutes until the cauliflower is partly cooked and excess moisture is gone.
Step 6: Mix the Sauce
In a bowl, stir together sour cream, mayo, cooled beef stock, mozzarella, Parmesan, and steak seasoning.
Step 7: Combine Everything
Add onion-cauliflower mixture to the dish.
Gently mix with beef and mushrooms.
Pour the sauce over and stir until fully coated. Smooth the top.
Step 8: Add Cheese and Bake
Sprinkle with remaining 1 cup mozzarella.
Bake for 30–40 minutes until hot and the top is golden and bubbling.
Step 9: Serve
Let cool for a few minutes, then serve hot. Leftovers store beautifully.
What to Serve It With
Simple side salad with lemon vinaigrette
Roasted Brussels sprouts or green beans
Steamed broccoli with a sprinkle of lemon zest
Garlic roasted asparagus
Crusty low-carb bread (if you’re not strict keto)
Variations / Substitutions
Ground turkey or chicken – Swap the beef for a lighter protein.
Add spinach – Stir in a handful of chopped spinach before baking.
No sour cream? – Try Greek yogurt for a protein boost.
Different cheese – Gouda or sharp cheddar add a twist.
Herb it up – Add thyme, rosemary, or parsley for freshness.
Storage & Leftovers
Fridge – Store in a sealed container for up to 5 days.
Reheat – Microwave individual portions or reheat in oven until hot.
Freeze – Wrap tightly and freeze for up to 2 months.
Meal prep tip – Portion into containers for ready-made lunches.
FAQs
Can I use frozen cauliflower rice?
Yes! Just make sure to cook off excess moisture before adding.
What if I don’t have bouillon paste?
You can use a standard beef bouillon cube or concentrated stock.
Can I skip the mayo?
Yes, though it adds creaminess. You can use all sour cream or a thick yogurt.
How do I make it spicier?
Add red pepper flakes or a spoonful of chili paste to the sauce.
Can I prep this in advance?
Yes! Assemble the casserole and refrigerate, then bake when ready.
What other mushrooms work?
White button or portobello work great in place of cremini.
Can I use shredded rotisserie chicken instead of beef?
Absolutely—just mix it in after sautéing the onions and cauliflower.
Final Thoughts
This Beef and Mushroom Cauliflower Casserole is cozy, creamy, and downright delicious.
It’s everything I love in a weeknight meal: bold, filling, and comforting without feeling too heavy.
Whether you’re feeding a family or meal prepping for the week, this casserole is one you’ll come back to again and again.
Beef and Mushroom Cauliflower Casserole
Ingredients
Method
- Preheat oven to 375°F (190°C). Grease a 13"x10" baking dish.
- Simmer bouillon with water until reduced to 1 tbsp. Let cool.
- Heat oil in skillet. Brown beef over medium-high heat. Transfer to baking dish.
- Sauté mushrooms in same skillet until browned and dry. Add to dish.
- Sauté chopped onion. Add cauliflower rice, steak seasoning, salt, and pepper.
- Cook 3 minutes on high.
- See full steps with tips & photos → https://theboatshedcafe.com/beef-and-mushroom-cauliflower-casserole/
Notes
- You can use frozen cauliflower rice—just make sure it’s thawed and drained well.
- Want extra flavor? Add garlic, fresh thyme, or crushed red pepper to the meat mixture.
- This casserole is naturally low-carb and gluten-free.
My name is Isabella, and this space was born from years of stirring sauces at sunset, baking cookies while the kids played on the porch, and finding comfort in a homemade meal after long, busy days. Here you’ll find delicious, reliable recipes made with simple ingredients, plus easy step-by-step photos and videos to help you cook confidently at home.