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Keto Zucchini Casserole

4.91 from 641 votes
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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 zucchinis.

zucchini casserole with sour cream
Table of contents

How To Make Keto Zucchini Casserole

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.

best zucchini casserole


Let’s see the simple ingredients to make your casserole flavorsome:

  • Zucchini – see next paragraph on how to prepare zucchinis to make the best zucchini casserole. Zucchinis 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.
best keto zucchini casserole

Making Keto Zucchini Casserole

There’s nothing complicated about making your own baked zucchini casserole. However, there are a few tips and tricks to make the best zucchini casserole.

A good cheesy casserole must be not watery with perfectly baked zucchini tender and not mushy.

So let me explain step-by-step how you can achieve perfection in your next zucchini casserole recipe.

keto vegetarian dinner

Drain the zucchini slices

This is the most important step to avoiding a watery zucchini casserole.

In fact, zucchinis are low-carb vegetables made of about 95% water! Incredible, right? This said it is crucial to extract the zucchini water before preparing your baked zucchini casserole.

Otherwise, the water will release into the pan, and you will end up with a watery, diluted cheese sauce. Not what we want, right!

To keep the zucchini crunchy in your gratin, first slice the zucchini with their skin on. Place the slices in a bowl with 1 teaspoon of salt and toss well.

The salt will naturally extract the liquid from the vegetables within 20 minutes. After this time, drain and pat dry with absorbent paper.

Baking dish size

The key to making a good casserole is to bake all the ingredients at the same speed. Therefore, the size of the baking dish matter.

How do you check the size of a baking dish? Well, always look at the volume of your pan, not the size!

In fact, not all pans of a similar size have the same height, and as a result, the volume of vegetables you will be able to fit in would be different.

This will impact the baking time, and texture and can end up in an overcooked casserole.

So, always check the volume of your baking dish. It is pretty simple to fill in the baking dish with water and see how much it can take.

As a rule of thumb, I am using a 1.5-liter (50-fluid-once or 6-cup) glass pan for zucchini casserole.

A square size is always the best to fit the length of one zucchini in a row.

keto zucchini casserole

Lay the zucchinis in rows

That’s the next important part of making this keto zucchini casserole right: lay the zucchini in rows.

This is not to make it pretty at all! It is all about cooking the zucchini slices simultaneously and ensuring we get the same uniform texture on the whole dish.

Look at the pictures below to see how I overlap the zucchini slices in single rows. As you can see, there is no layer of zucchini.

As a result, you won’t have to worry about the bottom zucchinis getting mushy, and overbaked compared to the top ones.

How To Make Keto Cheesy Zucchini Casserole

Spreading the cheese sauce

This zucchini and cheese casserole has a thick creamy sauce made with sour cream. Therefore, it’s not runny, but instead, it’s deliciously thick and cheesy.

That’s why you must use a spatula or spoon to spread the thick cheese sauce evenly over the top of the zucchini slices. This will ensure a consistent cheesy flavor.

Sprinkling more cheese

This is a keto cheesy zucchini casserole, so I believe there’s never too much cheese.

But hey, this is up to you. You can always decrease the amount of cheese slightly on top of your casserole, depending on your taste.

keto cheesy zucchini casserole

Bake 15 minutes until cheese broils

That is the last crucial step. Baked zucchini casseroles require minimal baking time to avoid mushy zucchinis.

As a result, only 15-20 minutes are required to make the best zucchini casserole.

Whether you make it keto or not, this is the best baking time. Then, how do you know if the casserole is good?

A casserole is ready when the cheese is broiled on top if some bubbles form on the sides of the dish, and if the vegetables are passing the knife test, they must be soft but still tender.

zucchini and cheese casserole
Keto-Baking-Guide-Best-Bread-Recipes Carine Grab my Keto Meal Plans! Use one of my many keto meal plans to reach your health goals!

More Keto Casserole Recipes

Below I listed my best low carb casserole recipes for you to try

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Keto Zucchini Casserole

6.6gNet Carbs
This Keto Zucchini Casserole is a cheesy keto dinner or side dish full of healthy low-carb vegetables and sour cream for only 6.6g of net carbs.
Prep: 30 minutes
Cook: 15 minutes
Total: 45 minutes
Yield: 6 servings
Serving Size: 1 serving
4.91 from 641 votes


  • 2 pounds Zucchini 4 large zucchinis
  • 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
This recipe may contain Amazon or other affiliate links. As an Amazon Associate I earn from qualifying purchases.


  • Preheat oven to 425°F (220°C). Grease a 1.5-liter square glass or ceramic baking dish with butter. Set aside.
  • Slice the zucchinis into 1/4 inch thick (0.6 cm), place 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 the slices 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 and stir until the cheese is fully melted and it 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 1520 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.


  • Store in the fridge in an airtight container for up to 4 days. Rewarm in a saucepan or the microwave.
  • Freeze in a single-serve airtight container for easy single meal serve. Defrost in the fridge the day before and rewarm in the microwave or saucepan.
Tried this recipe?Mention @sweetashoneyrecipes
Serving Size: 1 serving
Yield: 6 servings
Serving: 1servingCalories: 298.4kcal (15%)Carbohydrates: 8.3g (3%)Fiber: 1.7g (7%)Net Carbs: 6.6gProtein: 13.4g (27%)Fat: 24.3g (37%)Saturated Fat: 14.6g (91%)Cholesterol: 76.6mg (26%)Sodium: 1216mg (53%)Potassium: 491.4mg (14%)Sugar: 5.1g (6%)Vitamin A: 1100.3IU (22%)Vitamin C: 28.4mg (34%)Calcium: 342.2mg (34%)Iron: 0.8mg (4%)
Carine Claudepierre

About The Author

Carine Claudepierre

Hi, I'm Carine, the food blogger, author, recipe developer, published author of a cookbook and many ebooks, 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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    49 Thoughts On Keto Zucchini Casserole
    1 2
  1. I’m going to try this tomorrow night! I was thinking of adding ground beef to the casserole. Any suggestions?

  2. 5 stars
    Wow! Best recipe I ever tried and eaten in 40 years. Served to guests and they still rave about it months later. Thank you

  3. Hi I am out of heavy cream. Do you think I can substitute milk (and maybe a thickener?) for it? Thank you.

  4. 5 stars
    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!

  5. 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!

  6. 5 stars
    this was delicious! made it with marrow since didnt have zucchini. it was great! thanks for the recipe.

  7. 5 stars
    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!

  8. 5 stars
    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!

  9. 5 stars
    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

1 2


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