Keto Zucchini Casserole
By Carine Claudepierre
Published on 06/02/2020 - Last updated on 08/16/2024
This recipe may contain Amazon or other affiliate links. As an Amazon Associate I earn from qualifying purchases.
This easy, baked Keto Zucchini Casserole with cheese and sour cream is the best keto vegetarian meal or side dish. Plus, this healthy zucchini gratin is egg-free and gluten-free. The best keto casserole recipe for using all your summer zucchini.
A keto zucchini casserole is a low-carb casserole made with a cheesy wheat-free white sauce. In fact, most regular zucchini casseroles use a combination of milk, flour, and butter to create a thick white sauce.
However, milk and flour are not keto-friendly. Milk contains a lot of carbs and sugar from lactose, and flour is a high-carb ingredient.
So, the trick to achieving a similar texture is to make your zucchini casserole with sour cream, cream, and shredded hard cheese.
Ingredients and Substitutions
Let’s see the simple ingredients to make your casserole flavorsome:
- Zucchini – See next paragraph on how to prepare zucchini to make the best zucchini casserole. Zucchini are great keto-friendly vegetables with very low net carbs!
- Onion – fried onion is my French twist to this zucchini gratin! Soft, butter-fried onions are a delicious addition to the zucchini. However, you can skip them if you are not a fan of onions or can’t digest them very well.
- Garlic
- Salt
- Heavy cream – is a great keto-friendly dairy product with only 2.8 grams of carbs per 100 grams.
- Sour cream – sour cream is keto-friendly. It’s regular cream, just fermented with lactic acid bacteria resulting in a naturally sour cream perfect for thickening your keto sauce.
- Grated parmesan – the best cheese to add a strong cheesy, salty flavor to any gratin.
- Grated hard mozzarella – if you love strings in your sauce, mozzarella is the best choice.
How To Make Keto Zucchini Casserole
- Prep the Zucchini: Zucchini is 95% water, so removing excess moisture is crucial. Slice zucchini with skin on.
- Toss slices with 1 teaspoon of salt in a bowl.
- Let sit for 20 minutes to extract water. Drain and pat dry with paper towels.
- Choose the Right Baking Dish: Consider volume, not just length. Use a 1.5-liter (50-fluid-ounce or 6-cup) glass pan. Square dishes work best for even zucchini arrangement.
- Arrange Zucchini Properly: Lay slices in single, overlapping rows. Avoid multiple layers to ensure even cooking.
- Apply Cheese Sauce Correctly: Use a thick, creamy sauce made with sour cream. Spread evenly with a spatula or spoon for consistent flavor.
- Add Cheese Topping: For a keto version, be generous with cheese. Adjust amount to personal preference.
- Bake Carefully: Bake for only 15-20 minutes to prevent mushiness. Casserole is done when cheese is broiled on top, bubbles form on the sides, and zucchini is soft but still tender (use knife test).
Expert Tips
- Zucchini selection: Choose firm, medium-sized zucchini for best results. Overly large zucchini can be watery and less flavorful.
- Uniform slicing: Use a mandoline slicer for even zucchini slices, ensuring consistent cooking throughout the dish.
- Salt alternative: If you’re watching sodium intake, you can use a salt-free seasoning blend to extract moisture from the zucchini.
- Cheese variations: Experiment with different cheese combinations like Gruyère, fontina, or smoked gouda for unique flavor profiles.
- Adding Herbs: Add fresh herbs like thyme, basil, or oregano to the cheese sauce for an extra layer of flavor.
- Crispy Topping: For added texture, mix some crushed pork rinds or almond flour with grated Parmesan and sprinkle on top before baking.
- Make-ahead option: Prepare the casserole up to the point of baking, cover, and refrigerate for up to 24 hours before baking.
- Leftover tip: Leftover casserole can be reheated in a skillet to crisp up the bottom for a delicious next-day meal.
- Vegetable variation: Try mixing in other low-carb vegetables like bell peppers or spinach for added nutrition and color.
- Protein boost: For a heartier meal, add cooked, crumbled bacon or shredded rotisserie chicken to the cheese sauce.
More Keto Zucchini Recipes
Below I listed my best low carb casserole recipes for you to try
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Keto Zucchini Casserole
Ingredients
- 2 pounds Zucchini 4 large zucchini
- 1 teaspoon Salt
- 2 tablespoons Unsalted Butter melted or olive oil + 1 tablespoon to grease dish
- 2 oz Onion peeled, sliced
- 3 Garlic Clove
- ½ cup Heavy Cream
- ½ cup Sour Cream
- 1 cup Shredded Parmesan divided
- 1 cup Grated Mozzarella divided (or old mature cheddar or Emmental)
- 1 teaspoon Salt
Instructions
- Preheat the oven to 425°F (220°C). Grease a 1.5-liter square glass or ceramic baking dish with butter. Set aside.
- Slice the zucchini into 1/4 inch thick (0.6 cm), place them on a large bowl, sprinkle 1 teaspoon salt all over the slices and toss with your hands to bring the salt in contact with all slices. Set aside 20 minutes. This step will extract the zucchini water and prevent a watery casserole, don't skip!
- Drain the zucchini slices, then lay them onto absorbent paper and pat dry with more absorbent paper to remove as much excess water as you can.
- In a large saucepan, melt butter over medium heat and fry onions until fragrant and soft. Stir in garlic, pour heavy cream, sour cream, and keep cooking until it forms bubbles on the sides.
- Stir in half of the grated parmesan and half of the grated mozzarella until the cheese is fully melted and forms a cheesy sauce.
- Lay the zucchini slices in a row into the square baking dish. See the picture in my post or watch the video to see how to make this.
- Pour the cheese sauce and top of the zucchini and spread evenly to cover all the zucchini slices. Sprinkle the rest of the parmesan and mozzarella cheese all over the zucchini slices.
- Bake for 15–20 minutes or until cheese is broiled on top, the sauce bubbles in the pan, and zucchini are tender. Don't overbake, or the zucchini will become mushy.
Notes
Tools
Getting Started What Is Keto? Macro Calculator Sweetener Converter Intermittent Fasting Keto Fruits Keto Vegetables Keto Flours Fighting Keto Flu Healthy SweetenersWant My Kitchen Equipment?
Nutrition
About The Author
Hi, I'm Carine, the food blogger, author, recipe developer, published author of a cookbook, and founder of Sweet As Honey.
I have an Accredited Certificate in Nutrition and Wellness obtained in 2014 from Well College Global (formerly Cadence Health). I'm passionate about sharing all my easy and tasty recipes that are both delicious and healthy. My expertise in the field comes from my background in chemistry and years of following a keto low-carb diet. But I'm also well versed in vegetarian and vegan cooking since my husband is vegan.
I now eat a more balanced diet where I alternate between keto and a Mediterranean Diet
Cooking and Baking is my true passion. In fact, I only share a small portion of my recipes on Sweet As Honey. Most of them are eaten by my husband and my two kids before I have time to take any pictures!
All my recipes are at least triple tested to make sure they work and I take pride in keeping them as accurate as possible.
Browse all my recipes with my Recipe Index.
I hope that you too find the recipes you love on Sweet As Honey!
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Disclaimer
The recipes, instructions, and articles on this website should not be taken or used as medical advice. You must consult with your doctor before starting on a keto or low-carb diet. The nutritional data provided on Sweetashoney is to be used as indicative only.
The nutrition data is calculated using WP Recipe Maker. Net Carbs is calculated by removing the fiber and some sweeteners from the total Carbohydrates. As an example, a recipe with 10 grams of Carbs per 100 grams that contains 3 grams of erythritol and 5 grams of fiber will have a net carbs content of 2 grams. Some sweeteners are excluded because they are not metabolized.
You should always calculate the nutritional data yourself instead of relying on Sweetashoney's data. Sweetashoney and its recipes and articles are not intended to cure, prevent, diagnose, or treat any disease. Sweetashoney cannot be liable for adverse reactions or any other outcome resulting from the use of recipes or advice found on the Website.
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Swapped sour cream for cream cheese. Thickened very well. Great recipe for a keto side. Thank you.
👍
I added some pulled rotisserie chicken under the zucchini, this recipe was great!
Can you make this few hours ahead or night before
Absolutely, you can refrigerate the cooked casserole, foil the pan and rewarm the next day.
I’m going to try this tomorrow night! I was thinking of adding ground beef to the casserole. Any suggestions?
It would definitely work! I’d pre-cook it in a pan with seasoning for a few minutes before adding to the casserole.
OK great! Thank you! I’m also wondering..is the 2 oz of onion correct? It’s not much….
Yes it is, a small onion weight 4 oz so its about half an onion which is not that much. Feel free to reduce that amount to your liking of course!
Can I substitute creme fraiche in this recipe? Thank you!!!
I am sure it will taste amazing
Wow! Best recipe I ever tried and eaten in 40 years. Served to guests and they still rave about it months later. Thank you
Can you use frozen zucchini slices??? I have a bag full in my freezer
Probably but they often release lots of water in casserole and the sauce is less creamy. Maybe thaw them before to discard juice from zucchinis
Hi I am out of heavy cream. Do you think I can substitute milk (and maybe a thickener?) for it? Thank you.
Well milk will work but the sauce will be very thin, may be sprinkle 1/4 teaspoon of xanthan gum to thicken up!
Very good recipe. Unfortunately for me I had to use more yellow squash than zucchini as my zucchini didn’t look all that good. I did add a pinch of white pepper and Italian herbs. Was asked for the recipe. Nice amount for home or a small gathering. Thanks!
Hi! I am living in France, How can I find the heavy cream or sour cream? Do you have any recommendations?
Love your recipes and your site!
Creme liquide correspond a heavy cream et sour cream correspond a la creme epaisse. A bientot!
Casserole is delicious!!!
this was delicious! made it with marrow since didnt have zucchini. it was great! thanks for the recipe.
This was so amazingly good… and I don’t like zucchini!! Really was super yummy!
This was AMAZING! I love the flavor of the sauce. I think it would also be good with a dash of nutmeg or a little tarragon, but it’s not necessary. It’s SO good, just the way it is!
What is the size of a serving of lasagne per 8.3 carbs a serving?
Serving size is before the ingredient list. Scroll up
This recipe was delicious, my non-keto fam loved it too! The cheese sauce was fantastic – added a pinch of freshly ground nutmeg, allspice, mediterranean herbs, salt and pepper, and it tasted almost like bechamel! Thanks for sharing the recipe and for your wonderful site!
Do you have to use Parmesan cheese or could you just use mazarella cheese?
Sure, any hard grated cheese you love
Loved the flavour of this casserole. I used a food processor to slice the zucchini and they turned out too thin. I will slice them thicker next time
How much is considered as one serving?really trying to keep track and don’t want to go over.
Serving size appears before the ingredients list, enjoy