If you’re craving something hearty, cheesy, and low in carbs, this Italian Sausage and Pepper Casserole is the answer. Juicy Italian sausage, colorful bell peppers, rich marinara, and bubbly mozzarella come together in one skillet for a cozy, satisfying dinner. It’s ideal for anyone on a keto or gluten-free diet, perfect for meal prep, and made with ingredients you probably already have on hand.
Customizable and crowd-pleasing, it’s great on its own or served over zucchini noodles, cauliflower rice, or paired with a green salad. It’s everything you love about classic Italian flavors—just lighter, healthier, and easier to make.
What Is Italian Sausage and Pepper Casserole?
Italian Sausage and Pepper Casserole is a rich, comforting oven-baked dish that brings together bold Italian flavors and simple pantry ingredients for a meal everyone will love. It features juicy Italian sausage, colorful bell peppers, and caramelized onions all simmered in a flavorful marinara sauce, then baked until bubbling with melted mozzarella and Parmesan on top.
Inspired by the classic sausage and peppers skillet, this cozy casserole turns that well-loved combo into a cheesy, baked one-pan dinner that’s ideal for busy weeknights, Sunday meal prep, or feeding a hungry table with minimal effort.
The best part? This dish is naturally keto-friendly, low carb, and gluten-free, so it works for just about any lifestyle. Serve it as-is or spoon it over cauliflower rice, zucchini noodles, or your favorite low carb base for a complete meal that’s satisfying, flavorful, and always a hit.
Why I Think You’ll Love This Italian Sausage and Pepper Casserole
- Packed with bold flavor – Juicy sausage, sweet peppers, marinara, and gooey cheese in every bite.
- Low carb and gluten-free – Perfect for keto or anyone cutting back on carbs.
- A one-pan meal – Everything cooks in one skillet, bakes in one dish, and tastes amazing.
- Perfect for meal prep – It stores and reheats beautifully for quick, tasty leftovers.
- Easy to customize – Use mild or spicy sausage, switch up the cheese, or serve it over cauliflower rice, zoodles, or on its own.
Ingredients I Use (And Why They Matter)
Choosing high-quality, low-carb ingredients is the key to making this Italian sausage and pepper casserole both comforting and keto-friendly. Each element adds flavor, texture, and richness to this easy weeknight dinner. Here’s what I use and exactly why each one earns its spot:
- Italian Sausage – This is the star. I use mild or spicy pork sausage with no added sugar to keep it keto-friendly. I always remove the casings so the sausage can crumble and mix beautifully with the veggies.
- Onion – I go with yellow onion for its mellow sweetness, sliced thin so it cooks down quickly. Red onion works too if you like a bit more bite.
- Bell Peppers – A mix of red, yellow, and green bell peppers adds vibrant color and a balance of sweet and earthy flavors. Cut into 1-inch chunks—they hold their shape while baking and bring a satisfying texture.
- Garlic Cloves – Fresh garlic brings out that signature Italian depth of flavor. Mince finely and sauté just until fragrant—about 30 seconds—to avoid bitterness.
- Olive Oil – A drizzle of extra virgin olive oil helps caramelize the vegetables and boosts the Mediterranean feel of the casserole. It’s also packed with healthy fats and antioxidants.
- Marinara Sauce – Use a thick, sugar-free marinara sauce—either homemade or store-bought. Look for jars labeled “no sugar added” or “low-carb” to keep it keto-friendly. A robust sauce helps coat all the ingredients without becoming watery.
- Italian Seasoning – Use our homemade recipe for Italian Seasoning to give this dish authentic Italian flavors.
- Salt & Pepper – Since the sausage and cheese add salt, I season lightly and adjust to taste with sea salt and fresh cracked pepper.
- Mozzarella Cheese – Go for whole milk shredded mozzarella to achieve that classic melted and golden top. It creates the stretchy, cheesy finish that makes this dish irresistible. Fresh mozzarella can work too, but be aware it adds extra moisture.
- Parmesan Cheese – A final sprinkle of freshly grated Parmesan adds a nutty, salty layer that finishes the dish off perfectly. I skip the pre-shredded stuff for better flavor and melt.
How To Make Italian Sausage and Pepper Casserole
You will be surprised to see how easy it is to prepare this delicious casserole. Here is everything you need to do:
Preheat the Oven
I start by setting the oven to 375°F (190°C) so it’s ready to go by the time I finish assembling everything.
My tip: Lightly grease a 9×13-inch baking dish with olive oil or nonstick spray. It keeps the casserole from sticking and makes cleanup quicker.
Brown the Italian Sausage
In a large skillet over medium heat, I add the Italian sausage after removing the casings.
I break it up with a wooden spoon while it cooks, and keep stirring until it’s nicely browned and fully cooked, about 6 to 8 minutes. If there’s extra grease in the pan, I drain it off before moving on.
Kitchen Note: Browning adds deep, savory flavor—don’t rush this step!
Once it’s done, I transfer the sausage to a bowl and set it aside. No need to clean the skillet — we’re using those delicious browned bits for the veggies.
Sauté the Veggies
Using the same skillet, add 1 tablespoon of olive oil.
Add the sliced onion and chopped bell peppers (red, green, yellow). Sauté for 5–6 minutes, stirring occasionally, until they’re soft and just starting to caramelize.
Add the minced garlic and cook for an additional 30 seconds, until fragrant.
Tip: Garlic burns fast, so I keep an eye on it and stir gently until it’s just fragrant.
Build the Flavor
Return the cooked sausage to the skillet with the sautéed veggies.
Stir in the marinara sauce, Italian seasoning, salt, and black pepper until everything is well combined.
Simmer for a minute or two to let the flavors mingle.
Assemble the Casserole
Pour the sausage and pepper mixture into your greased baking dish.
Sprinkle shredded mozzarella and grated Parmesan evenly over the top.
Want a crispier topping? Add a little extra Parmesan for golden edges!
Bake to Perfection
I pop the dish into the preheated oven uncovered and bake for 15 to 20 minutes, or until the cheese is melted, bubbly, and just starting to turn golden in spots.
Keep an eye on it during the last few minutes for that perfect cheesy finish.
Garnish & Serve
Let it cool slightly, then garnish with fresh basil or parsley for a pop of color and freshness.
Serving Ideas
This casserole is rich, cheesy, and full of bold Italian flavor, so it’s easy to pair with a variety of sides. Whether you’re keeping it low carb or adding a little comfort on the side, here are some of my favorite ways to enjoy it:
- Over Zucchini Noodles – Keep it low-carb and fresh by serving the casserole over sautéed or spiralized zoodles. A great way to soak up that cheesy sauce!
- With Cauliflower Rice – Scoop the casserole over steamed cauliflower rice for a grain-free, veggie-packed option that still feels hearty.
- With Crusty Bread or Garlic Toast – For a cozy, carb-loving meal, serve it alongside warm, toasted ciabatta, sourdough, or garlic bread to mop up every drop of sauce.
- Tossed with Pasta – Mix leftovers into cooked penne, rigatoni, or farfalle for an easy baked pasta dish the next day.
- Paired with a Crisp Salad – Balance the richness of the casserole with a light green salad dressed in lemon vinaigrette or balsamic for a fresh contrast.
- Meal Prep Bowls – Layer portions into meal prep containers with a veggie base like spinach or sautéed kale for easy, heat-and-eat lunches.
Storage & Reheating Tips
Once the casserole has cooled to room temperature, transfer leftovers to an airtight container or cover the baking dish tightly with foil or a lid.
Freezer: Freeze individual portions or the full casserole for up to 2 months. Use freezer-safe containers and label with the date for easy grab-and-reheat meals.
Fridge: Store in the refrigerator for up to 4 days.
How to Reheat It
There are a few ways to reheat this Italian sausage and pepper casserole, depending on your time and portion size:
- Oven (best for full casseroles) – Preheat the oven to 350°F (175°C). Cover the dish with foil and bake for about 15 to 20 minutes, or until heated through.
- Microwave (great for individual portions) – Place a serving in a microwave-safe dish and heat for 2 to 3 minutes, stirring halfway through. Add a splash of water or sauce if it looks dry.
- From Frozen – Thaw in the fridge overnight for best results. Reheat using the oven or microwave instructions above. If reheating from frozen, add extra baking time (about 10 to 15 minutes) in the oven.
More Casserole Recipes
Italian Sausage and Pepper Casserole
Description
Ingredients
- 1 lb Italian sausage mild or spicy, casings removed
- 1 yellow onion medium, thinly sliced
- 1 red bell pepper cut into 1″ pieces
- 1 green bell pepper cut into 1″ pieces
- 1 yellow pepper cut into 1″ pieces
- 3 cloves garlic minced
- 1 tbsp olive oil
- 1 cup marinara sauce low-carb if needed
- 1 tsp Italian seasoning
- ½ tsp salt or to taste
- ¼ tsp black pepper
- 1½ cups mozzarella cheese shredded
- ¼ cup Parmesan cheese grated
- Optional: fresh basil or parsley for garnish
Instructions
- Preheat your oven to 375°F (190°C). Lightly grease a 9×13" baking dish or casserole pan.
- In a large skillet over medium heat, cook the Italian sausage until browned and fully cooked, breaking it up with a spoon. Transfer to a bowl and set aside.
- In the same skillet, add olive oil, then sauté the onion and bell peppers until they’re soft and slightly caramelized (about 5-6 minutes). Add minced garlic and cook for another 30 seconds until fragrant.
- Add the cooked sausage back to the pan with the veggies. Stir in marinara sauce, Italian seasoning, salt, and pepper.
- Transfer the sausage and pepper mixture into the prepared baking dish. Sprinkle mozzarella and Parmesan evenly on top.
- Bake uncovered for 15–20 minutes, or until the cheese is bubbly and golden brown.
- Garnish with fresh basil or parsley if desired. Serve hot on its own, over zucchini noodles, cauliflower rice, or with crusty bread if not low-carb.
How do we calculate the nutrition info?
These nutrition facts listed are determined using nutrition information from the USDA Food Database. Our nutrition facts are accurate, but if you are using different products, please make your calculations. Net carb count is calculated by subtracting both fiber and sugar alcohols because they don’t raise blood sugar.
Absolutely delicious!