Ground Beef Cauliflower Casserole

The winter my husband started keto, I spent weeks experimenting with cauliflower replacements. Most nights ended with disappointed sighs and takeout menus. Then this casserole happened, and suddenly nobody was missing the pasta anymore.

My sister-in-law stayed over during those recipe-testing months, and when she took her first bite, she actually asked what restaurant wed ordered from. Watching her go back for thirds while I told her it was cauliflower made all those failed attempts worth it.

Ingredients

• 1 lb lean ground beef: Drain the fat after browning, otherwise the casserole ends up greasy and heavy
• 1 medium onion, finely chopped: The smaller you dice, the more they melt into the background instead of staying chunky
• 3 cloves garlic, minced: Fresh garlic makes such a difference here, don't be tempted by the jarred stuff
• 4 cups cauliflower rice: If using frozen, thaw and squeeze out excess moisture or the casserole gets watery
• 1 medium red bell pepper, diced: Adds this subtle sweetness that balances the beef perfectly
• 1 cup baby spinach, chopped: Totally optional, but I love how it wilts down and sneaks in extra greens
• 1 cup sour cream: Full fat works best for the creamiest texture
• 1 cup shredded cheddar cheese: Reserve half for the filling and half for that golden topping
• 1/2 cup shredded mozzarella cheese: This creates the beautiful cheese pull effect
• 2 tbsp olive oil: Use this to sauté your veggies first
• 1 tsp dried oregano: Dried herbs work beautifully here since they'll cook in the beef
• 1 tsp dried basil: The combo of oregano and basil gives it that Italian-American comfort food vibe
• 1/2 tsp smoked paprika: This is my secret ingredient, adds depth without making it spicy
• 1/2 tsp salt and black pepper: Taste the filling before adding more, the cheese is already salty
• 1/4 tsp crushed red pepper flakes: Skip these if you're sensitive to heat
• 2 tbsp fresh parsley, chopped: Adds this pop of color and freshness at the end

Instructions

Get your oven ready:

Preheat to 375°F and grab your 9x13 baking dish, giving it a quick spray with cooking spray

Sauté the vegetables:

Heat olive oil in a large skillet over medium heat, cooking onion and red bell pepper for 3-4 minutes until they soften

Add the garlic:

Throw in minced garlic and stir constantly for 1 minute so it doesn't burn

Brown the beef:

Add ground beef, breaking it apart with your spatula, and cook 5-7 minutes until no pink remains

Season the meat:

Sprinkle in oregano, basil, smoked paprika, salt, pepper, and red pepper flakes, stirring until fragrant

Cook the cauliflower:

Stir in cauliflower rice and spinach, cooking 4-5 minutes until tender and any liquid has evaporated

Make it creamy:

Remove from heat and fold in sour cream with half the cheddar until everything's coated

Transfer to baking dish:

Spread the mixture evenly into your prepared baking dish

Add the cheesy topping:

Sprinkle remaining cheddar and all the mozzarella over the top

Bake until golden:

Pop in the oven for 20 minutes until the cheese is bubbling and has those gorgeous browned spots

Rest and serve:

Let it sit 5 minutes so it sets up, then scatter parsley on top and serve warm

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This became our Sunday meal prep staple because it reheats so beautifully. My coworkers started asking what smelled so good when I'd warm it up at the office.

Making It Your Own

I've swapped ground turkey for beef when we wanted something lighter, and honestly, nobody noticed the difference. Mushrooms add this earthy quality that pairs surprisingly well with the smoked paprika.

What To Serve With It

A crisp green salad with a vinaigrette cuts through all that rich cheese perfectly. Sometimes I'll roast some broccoli on the side sheet pan while the casserole bakes.

Storage And Reheating

This keeps in the fridge for up to 5 days and actually tastes better the next day. You can also freeze it for up to 3 months, just thaw overnight before reheating.

• Reheat covered at 350°F for about 20 minutes if frozen
• Microwave individual portions for 2-3 minutes, stopping to stir halfway
• Add a splash of water before reheating if it seems dry

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There's something so satisfying about serving a casserole that feels indulgent but fits your lifestyle. Hope this becomes a weeknight favorite in your house too.

Recipe Questions & Answers

→ Can I make this ahead of time?

Yes, assemble the dish up to 24 hours in advance and refrigerate. When ready to bake, add 5-10 minutes to the cooking time if baking from cold.

→ What can I substitute for ground beef?

Ground turkey, chicken, or even plant-based crumbles work well. Lean options may require a splash of olive oil to prevent drying.

→ Is this freezer-friendly?

Absolutely. Wrap the unbaked casserole tightly and freeze for up to 3 months. Thaw overnight in the refrigerator before baking.

→ How do I prevent the cauliflower from becoming mushy?

Avoid overcooking during the stovetop phase—just 4-5 minutes until tender. Any excess liquid should evaporate before adding the dairy.

→ Can I use frozen cauliflower rice?

Yes, frozen works perfectly. No need to thaw first—just cook it slightly longer to evaporate the extra moisture that occurs during freezing.

→ What vegetables can I add?

Mushrooms, zucchini, or diced broccoli complement the flavors beautifully. Add them when sautéing the peppers so they cook through.