Low Carb Keto Crustless Pizza Casserole

Last Tuesday, standing in front of the fridge at 6 PM, I realized I had zero energy for actual dinner but was craving pizza like nobody's business. That's when this casserole happened, and honestly, it's become one of those throw-together meals I make when I want something comforting but don't want to deal with dough or waiting for delivery.

My sister-in-law came over for dinner last month, skeptical of anything 'keto' or 'crustless' because she's a traditional pizza purist. She took one bite, looked at me, and said 'okay, I get it now.' We ended up eating the entire dish between the two of us while catching up, and she texted me the next day asking for the recipe.

Ingredients

• 1 lb ground Italian sausage: The spicy Italian variety gives you that authentic pizza flavor without needing a dozen different seasonings. Drain the fat if you want it lighter, but I keep a little for flavor.
• 20 slices pepperoni: Optional if you're keeping it super simple, but they get those crispy edges in the oven that remind you of actual pizza. Turkey pepperoni works great too.
• 1 cup sliced mushrooms: They release water as they cook, so don't skip the step where you sauté them first. No one wants a watery casserole.
• 1/2 cup diced green bell pepper: Adds that fresh crunch and sweetness. Red pepper works just as well if that's what you have.
• 1/2 cup diced onion: Sweet onion is my preference here, but yellow onion gets the job done perfectly fine.
• 2 cloves garlic, minced: Fresh garlic makes such a difference. The jarred stuff works in a pinch, but fresh gives you that real Italian kitchen smell.
• 1 cup sugar-free pizza sauce: Read your labels here, some 'sugar-free' sauces still have hidden carbs. Marinara works beautifully too.
• 2 cups shredded mozzarella cheese: The cheese that pulls and stretches. Low moisture mozzarella gives you that perfect golden-brown top.
• 1/2 cup shredded cheddar cheese: Adds that extra sharpness and depth. Sharp cheddar gives you more flavor with less cheese.
• 1/4 cup grated Parmesan cheese: The salty umami bomb on top. Don't use the canned stuff, get the real grated Parmesan if you can.
• 1 tsp dried Italian herbs: If you have fresh oregano and basil, use them, but the dried blend works perfectly for this kind of comfort food.
• 1/2 tsp salt and 1/2 tsp black pepper: Start here and adjust to taste. The sausage and cheese already bring salt to the party.
• Red pepper flakes: Add these if you like a little heat. They wake everything up without being overwhelming.

Instructions

Get your oven ready:

Preheat to 400°F and grab your 9x9 baking dish. Give it a quick spray with cooking oil or rub it with a little olive oil.

Brown the sausage:

Cook the Italian sausage in a large skillet over medium heat until it's fully browned, about 8-10 minutes. Break it up as it cooks so you get those nice crumbles. Drain the excess fat if there's a lot pooling.

Add the vegetables:

Toss in the mushrooms, bell pepper, onion, and garlic. Sauté everything together for 3-4 minutes until the vegetables soften and the kitchen starts smelling amazing.

Make it pizza-flavored:

Pour in the pizza sauce and add the Italian herbs, salt, and pepper. Let it simmer together for 2-3 minutes so all the flavors start hanging out and getting friendly.

Build the casserole:

Transfer the whole mixture to your prepared baking dish. Spread it out evenly so every bite will have the same ratio of meat to vegetables to sauce.

Add the cheese blanket:

Sprinkle the mozzarella and cheddar evenly over the top. Don't be shy with it. Then scatter the Parmesan on top and arrange the pepperoni slices if you're using them.

Bake until bubbly:

Pop it in the oven for 20-25 minutes. You'll know it's done when the cheese is melted and starting to turn golden brown in spots.

The hardest part:

Let it rest for 5 minutes before serving. This seems impossible when it smells this good, but it helps the casserole set so you get clean portions instead of a mess on your plate.

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This recipe became my go-to during busy weeks when I'm meal prepping for myself. There's something so satisfying about pulling a container out of the fridge and knowing I have something waiting for me that actually tastes like comfort food, not like 'diet food' at all.

Making It Your Own

The beauty of this casserole is how flexible it is. I've made it with ground beef when that's what was on sale, and honestly, it's just as good. Turkey or chicken work fine too, you might want to bump up the Italian seasoning a bit since those meats are milder than sausage.

Add-Ins That Work

Sometimes I throw in black olives, spinach, or roasted red peppers depending on what needs to get used up in the fridge. Just keep in mind that vegetables with high water content, like zucchini, should be cooked down first or they'll make your casserole soggy.

Serving Ideas

A crisp green salad with a simple vinaigrette cuts through all that rich cheese perfectly. If you're not strictly keto, some garlic bread on the side wouldn't hurt. My keto friends love it with cauliflower breadsticks.

• Double the recipe and bake it in a 9x13 pan for easy meal prep or feeding a crowd
• Leftovers reheat beautifully in the microwave for about 2 minutes
• Top with fresh basil or parsley right before serving for a pop of color

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Hope this becomes one of those recipes you turn to when you want something comforting but don't want to spend hours in the kitchen.

Recipe FAQs

→ Can I freeze this casserole?

Absolutely. Assemble the dish, cover tightly with foil and freeze for up to 3 months. Thaw overnight in the refrigerator, then bake at 400°F until heated through and bubbly.

→ What vegetables work best in this?

Mushrooms, bell peppers, and onions are classic choices, but you can also add black olives, roasted red peppers, spinach, or even zucchini. Just keep portions around 2 cups total to maintain the proper texture.

→ Is sugar-free pizza sauce necessary?

For strict keto or very low-carb diets, yes—traditional pizza sauce can contain 6-8 grams of sugar per serving. Look for marinara labeled sugar-free or use crushed tomatoes with Italian herbs for the best results.

→ Can I make this dairy-free?

You can use dairy-free cheese alternatives, though they may melt differently. Nutritional yeast combined with vegan shreds can help achieve a cheesy flavor. The texture will be slightly different but still satisfying.

→ How do I store leftovers?

Store in an airtight container in the refrigerator for 4-5 days. Reheat individual portions in the microwave for 2-3 minutes or in a 350°F oven until warmed through. The cheese remains beautifully melted after reheating.

→ Can I double this recipe?

Yes, simply double all ingredients and use a 9x13-inch baking dish instead of 9x9. You may need to increase baking time by 5-10 minutes to ensure the center is fully heated and the cheese is bubbly.