Chicken Spinach and Mushroom Low Carb Oven Casserole

Posted on October 9, 2025

Creamy Chicken Spinach and Mushroom Casserole

Looking for a low-carb, high-protein dinner option that’s not only comforting but also easy to prepare? This creamy chicken spinach and mushroom casserole is the ultimate weeknight solution. It’s rich, cheesy, and packed with vegetables, making it ideal for anyone following a keto, gluten-free, or low-carb diet. With a cook time under 30 minutes, it’s perfect for meal prep, quick dinners, or family gatherings.

What makes this dish stand out is its balance of flavor and nutrition. The chicken breast offers lean protein, while the spinach and mushrooms contribute essential vitamins and fiber. A creamy blend of mozzarella, Parmesan, and heavy cream creates that satisfying, cheesy finish without loading up on carbs. You can even explore more about the benefits of spinach and how it supports immune and digestive health.

As a bonus, the recipe is highly versatile. You can adjust it to your taste or dietary restrictions. Swap the dairy for a non-dairy alternative, or use chicken thighs instead of breasts for a richer flavor. Learn more about chicken as a protein source, especially its role in high-protein, low-carb meals. And if you’re exploring more oven-friendly keto recipes, check out our internal guide on easy low carb dinner casseroles for more inspiration.

Health Benefits of a Low-Carb, High-Protein Casserole

Choosing a low-carb, high-protein meal like this creamy chicken spinach and mushroom casserole supports a balanced lifestyle in several impactful ways. Whether you’re following a keto, gluten-free, or general low-glycemic diet, this dish aligns with your goals while delivering full-bodied flavor and comfort.

First, the use of lean chicken breast provides a high dose of protein with minimal fat, promoting muscle repair and satiety. Protein helps stabilize blood sugar levels and keeps you full longer, which is ideal for those managing weight or blood sugar. Explore more about the nutritional impact of chicken as food, especially in high-protein diets.

Second, spinach adds fiber, iron, and antioxidants, making it a powerhouse for digestive and immune health. This leafy green is not only low in carbs but also rich in vitamins A, C, and K. Learn more about the health benefits of spinach to understand its role in anti-inflammatory and heart-friendly diets. Combined with mushrooms, which are packed with B vitamins and known for their immune-boosting compounds, this casserole offers much more than just taste. You can even explore how mushrooms contribute to a balanced diet.

Additionally, the fats from olive oil, heavy cream, and cheese help support ketosis by providing necessary energy. These ingredients also improve the absorption of fat-soluble vitamins. If you’re following a ketogenic meal plan, understanding the basics of the ketogenic diet can further help you stay within your macro limits while enjoying hearty, satisfying dishes.

This casserole is naturally gluten-free, making it a smart option for those with Celiac disease or gluten sensitivity. Learn more about gluten-free diets to see why avoiding gluten can reduce inflammation and improve gut health, even for those without a diagnosed intolerance.

For those planning their weekly meals, this recipe also fits perfectly into batch cooking. It’s one of the top-rated options in our meal prep casseroles collection, loved for its ease of storage and reheating.

Ingredient Breakdown and Substitutions

This creamy chicken spinach and mushroom casserole is made with simple, pantry-friendly ingredients that work together to create a rich and comforting dish. Here’s a closer look at each component and how you can tweak it based on your dietary needs or flavor preferences.

Main Ingredients and Their Benefits:

Chicken Breasts: A lean protein that supports muscle repair and fullness. You can also use chicken thighs for more moisture and flavor if you’re not strictly watching fat intake.
Olive Oil: Adds heart-healthy fats and helps sauté ingredients without burning. See the benefits of olive oil for more insight into its nutritional value.
Spinach: This leafy green provides fiber, iron, and antioxidants. If fresh spinach isn’t available, frozen works just as well — just be sure to squeeze out excess water.

Mushrooms: Low in carbs and rich in umami flavor, mushrooms also support immune function. Learn more about mushroom nutrition.
Onion & Garlic Powder: Add aromatic depth to the dish while remaining low in carbs.
Heavy Cream: A keto-friendly ingredient that creates a rich, creamy sauce. You can substitute with coconut cream for a dairy-free version.

Parmesan & Mozzarella Cheese: Provide a savory, gooey topping and depth of flavor. For a sharper taste, consider mixing in sharp cheddar or Asiago.
Dried Thyme: A classic herb that enhances the earthy flavors of mushrooms and spinach.

Low-Carb Ingredient Substitutions:

Cream Cheese: Add 2 oz to the cream mixture for an extra thick and rich texture.
Kale or Swiss Chard: Substitute for spinach if you’re looking for different leafy greens with a stronger bite.

Dairy-Free Options: Use coconut cream, almond-based cheese, or nutritional yeast in place of traditional dairy.

Optional Add-Ins for Variety:

Sun-Dried Tomatoes: For a tangy twist that complements the creamy base.
Cooked Bacon: Adds smokiness and extra fat — ideal for keto meal plans.
Bell Peppers or Zucchini: Add crunch and boost the veggie content without raising the carb count significantly.

This dish aligns perfectly with other low carb dinner recipes featured in our collection of casserole dish ideas, and it’s easy to adjust based on what’s in your fridge. For those following a gluten-free lifestyle, all ingredients are naturally compliant, making this recipe a safe and satisfying choice.

For inspiration and similar dishes, you might also enjoy our internal roundup of low-carb weeknight oven bakes featuring variations with beef, turkey, and vegetarian options.

Kitchen Tools and Prep Tips

Making this low-carb chicken spinach and mushroom casserole doesn’t require any fancy equipment, which makes it a great choice for beginner cooks and busy weeknights. With just a few common kitchen tools, you can assemble this meal quickly and efficiently.

Essential Tools:

Large Skillet or Sauté Pan: For browning the chicken and cooking down the veggies. A non-stick or cast iron pan works best to avoid sticking and ensure even cooking.

Baking Dish (8×8 or 9×13): The size will depend on how thick you want the casserole. An 8×8 gives a thicker bake; a 9×13 will cook slightly faster.
Mixing Bowl: For combining the cream, Parmesan, and seasoning before pouring over the casserole base.
Silicone Spatula or Wooden Spoon: Helps mix without scratching non-stick surfaces.

Sharp Knife and Cutting Board: For prepping chicken, onions, and mushrooms quickly and safely.

Time-Saving Tips:

Use pre-sliced mushrooms and pre-washed spinach to reduce prep time.
Swap raw chicken for pre-cooked or rotisserie chicken if you’re in a rush—just add it when the spinach goes in, since it only needs to be heated.
Shred your own cheese for better meltability and fewer additives—pre-shredded often contains anti-caking agents that affect texture.

Prep in Advance:

You can prep the entire casserole ahead of time, refrigerate it unbaked for up to 24 hours, then bake it fresh.

Freeze the assembled dish before baking, then thaw overnight in the fridge and bake when ready.
Portion out leftovers in airtight containers for easy meal prep lunches throughout the week. Check out some of our top-rated meal prep casserole tips to stay organized and efficient in the kitchen.

By keeping these tools and strategies in mind, you’ll streamline your cooking process and make this low-carb weeknight casserole a repeat favorite in your meal rotation.

Step-by-Step Cooking Instructions with Pro Tips

This chicken spinach mushroom casserole is simple to assemble and loaded with flavor. Here’s how to bring it all together:

Preheat the Oven

Set your oven to 375°F (190°C). This moderate temperature ensures everything bakes evenly and the cheese gets that golden, bubbly top.

Sauté the Chicken

In a large skillet, heat 1 tablespoon of olive oil over medium heat.
Add sliced chicken breasts and season with salt, pepper, and 1 teaspoon of garlic powder.

Sauté until lightly browned. The chicken doesn’t need to be fully cooked yet—it will finish baking in the oven.

Add Aromatics and Vegetables

Stir in 1 small diced onion and 1 cup of sliced mushrooms.
Cook until both are softened—about 4-5 minutes.
Add 2 cups of fresh spinach and cook until just wilted.

Remove from heat.

Make the Creamy Mixture

In a separate bowl, whisk together ½ cup of heavy cream, ½ cup grated Parmesan, and ½ teaspoon dried thyme.
Mix until well combined. This is the sauce that will bring everything together.

Assemble the Casserole

Lightly grease a baking dish with olive oil or non-stick spray.
Transfer the cooked chicken and veggie mixture into the dish.

Pour the cream mixture over the top and gently stir to coat.
Sprinkle 1 cup of shredded mozzarella cheese evenly over everything.

Bake

Bake in the preheated oven for 20–25 minutes, or until the cheese is bubbly and lightly golden on top.

Rest and Serve

Let the casserole cool for 5 minutes before serving. This helps the sauce thicken slightly and makes it easier to portion.

Pro Tips:

For extra crispiness, broil the casserole for the final 2 minutes.
Want a thicker sauce? Add 2 ounces of cream cheese to the cream mixture.

Looking for a spice kick? Sprinkle with crushed red pepper flakes before serving.

This recipe is part of our featured low-carb dinner prep collection, where flavor meets function for the modern home cook.

Serving Suggestions and Pairings

This low-carb chicken spinach and mushroom casserole is satisfying on its own, but you can easily enhance the meal with a few keto-friendly sides or additions for variety.

Low-Carb Side Ideas:

Cauliflower Rice: A classic low-carb base that soaks up the creamy sauce.
Zucchini Noodles (Zoodles): Adds texture and keeps the dish light.

Steamed Broccoli or Asparagus: Balances the richness of the casserole with freshness.
Side Salad: A simple arugula or mixed greens salad with olive oil vinaigrette adds crunch and acidity.

Meal Prep Suggestions:

Portion out servings into containers with a scoop of cauliflower mash or green beans for balanced meals.
This dish holds up well in the fridge, making it perfect for lunches during the workweek.

Optional Toppings or Additions:

Fresh herbs like parsley or thyme

A sprinkle of red pepper flakes
A squeeze of lemon juice to brighten the flavors

For more inspiration, check out our favorite casserole pairings and meal prep trays.

Storage, Freezing, and Reheating Instructions

Keeping leftovers fresh and reheating them properly is key to enjoying this casserole multiple times.

Storage Tips:

Store in the refrigerator for up to 4 days in an airtight container.

Let the casserole cool completely before storing to avoid condensation and sogginess.

Freezing Instructions:

To freeze before baking: Assemble the dish, cover tightly with foil, and freeze. Thaw overnight in the fridge and bake as directed.
To freeze after baking: Cool completely, slice into portions, wrap, and freeze for up to 2 months.

Reheating Methods:

Oven: Reheat in a baking dish at 350°F for 10–15 minutes until heated through.
Microwave: Heat on medium for 1–2 minutes per portion. Stir halfway through for even heating.
For best texture, use the oven method to maintain the creamy consistency and crisp top layer.

This meal also works well for batch cooking, as featured in our go-to meal prep casseroles board.

Nutrition Facts and Macros (with Estimates)

While exact nutrition will vary slightly based on brands and measurements, here’s a breakdown per serving (assuming 6 servings):

Calories: ~390
Protein: ~32g
Fat: ~28g
Net Carbs: ~5g
Fiber: ~1g

Macronutrient Highlights:

High in protein from chicken and cheese
Moderate to high in fat, ideal for ketogenic diets
Low in carbohydrates, making it suitable for low-carb meal plans
Gluten-free, with no wheat-based thickeners or ingredients

If you’re tracking your macros for keto or low-carb plans, this dish fits seamlessly into your daily intake. It’s also included in our gluten-free low-carb recipe roundup for easy reference.

Variations: Customize Your Low-Carb Casserole

This casserole is incredibly versatile, and you can easily modify it to suit your taste, dietary preferences, or available ingredients.

Add-Ins:

Cooked Bacon or Pancetta: Adds a smoky, savory flavor and boosts fat content for keto diets.
Sun-Dried Tomatoes: A tangy element that cuts through the creamy texture.
Bell Peppers or Zucchini: Adds crunch and a fresh veggie contrast.

Protein Swaps:

Use ground turkey or shredded rotisserie chicken for convenience.
For a vegetarian option, replace chicken with tofu, tempeh, or extra mushrooms.

Dairy-Free Modifications:

Replace heavy cream with coconut cream
Use dairy-free shredded cheese or nutritional yeast to replicate the cheesy flavor.

Spice Up the Flavor:

Add paprika, Italian seasoning, or red pepper flakes to the cream sauce.
Mix in a spoonful of mustard for a tangy punch.

To explore more variations and crowd-pleasing options, visit our curated board of creative casserole dishes.

FAQs

Can I use frozen spinach instead of fresh?
Yes, frozen spinach works perfectly. Just thaw it first and squeeze out excess water to avoid a watery casserole.

Is this casserole good for keto meal prep?
Absolutely. It’s high in protein and fat, low in carbs, and reheats well — making it ideal for weekly keto meal prep.

How do I thicken the sauce if it’s too runny?
You can add 2 oz of cream cheese to the cream mixture or sprinkle a bit of xanthan gum before baking.

Can I make this casserole ahead of time?
Yes, you can assemble the casserole and refrigerate it unbaked for up to 24 hours. Bake when ready.

What can I substitute for heavy cream?
Coconut cream is a great dairy-free substitute. You could also use a blend of Greek yogurt and milk, though it may be slightly tangier.

Is this dish gluten-free?
Yes. All the ingredients are naturally gluten-free, making it safe for those with gluten sensitivities.

Can I use chicken thighs instead of breasts?
Yes, chicken thighs offer more flavor and stay moist during baking. They’re a great alternative if you’re not avoiding fat.

How do I make this dairy-free?
Swap the heavy cream with coconut cream, and use plant-based cheese alternatives or nutritional yeast.

What’s the best way to reheat leftovers?
The oven works best to keep the texture intact. Microwave works in a pinch, but it may soften the topping.

Can I freeze this casserole?
Yes. You can freeze it before or after baking. Just make sure it’s fully cooled before freezing and tightly wrapped.