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Keto zucchini casserole

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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.

zucchini casserole with sour cream

Keto zucchini casserole ingredients

A keto zucchini casserole is 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.

best zucchini casserole

So, the trick to achieve a similar texture is to make your zucchini casserole with sour cream, cream and shredded hard cheese. 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 onion or can’t digest them very well.
  • Garlic
  • Salt
  • Heavy cream
  • Sour cream – sour cream is keto-friendly. It’s regular cream, just fermented with lactic acid bacteria resulting in a naturally sour cream perfect to thicken your keto sauce.
  • Grated parmesan – the best cheese to add a strong cheesy salty favor to any gratin.
  • Grated hard mozzarella – if you love strings in your sauce, mozzarella is the best choice.

best keto zucchini casserole

How to make 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 avoid a watery zucchini casserole. In fact, zucchinis are low-carb vegetables made of about 95% of water! Incredible, right? So this said, it means that it is very important to extract the zucchini water before preparing your baked zucchini casserole. Otherwise, the water will release in the pan and you will end up with a watery, diluted cheese sauce. Not what we want right! So, to keep the zucchini crunchy in your gratin, first slice the zucchini with their skin on. Place the slices on 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 make a good casserole is to bake all the ingredients at the same speed. Therefore, the size of the baking dish matter. So 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 with 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. I am repeating myself but this will impact the baking time, texture and can end up with an overcooked casserole. So, always check the volume of your baking dish. It is pretty simple to do so, 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 at the same speed and to ensure we get the same uniform texture on the whole dish. Look at my 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 bottom zucchinis getting mushy, overbaked compared to the top ones.

How To Make Keto Cheesy Zucchini Casserole

Evenly spread 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 a 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.

Sprinkle 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 slightly the amount of cheese 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? Well, a casserole is ready when 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

More keto vegetarian meals

This is a great vegetarian keto meal or side dish to accompany grilled meat. Others delicious vegetarian dishes you can enjoy on keto are:

Brussel sprouts with mustard sauce
Roasted Brussel sprouts with mustard sauce. Crispy baked brussel sprouts covered with a creamy shallots mustard sauce
Net Carbs: 6.5g per serving | Serves 6
10 minutes
Check out this recipe
Keto spinach quiche
A flakey, buttery, almond flour quiche crust filled with a moist cheesy spinach egg filling
Net Carbs: 4.4g per serving | Serves 8
20 minutes
Check out this recipe
keto spinach quiche

Made this cheesy zucchini casserole and want to share your feedback, question or a picture of your creation with me? Join me in my Facebook Support Group. I see you there.

XOXO Carine
zucchini casserole with sour cream

Keto zucchini casserole

A cheesy keto zucchini casserole with sour cream
Prep Time: 30 mins
Cook Time: 15 mins
Total Time: 45 mins
6 serve
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  • 2 pounds Zucchini 4 large zucchini
  • 1 teaspoon Salt
  • 2 tablespoons Butter , melted or olive oil + 1 tablespoon to grease dish
  • 2 oz Onion , peeled, sliced
  • 3 Garlic clove
  • 1/2 cup heavy cream
  • 1/2 cup sour cream
  • 1 cup Grated Parmesan divided
  • 1 cup Grated Mozzarella divided (or old mature cheddar or Emmental)
  • 1 teaspoon Salt
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  • Preheat oven to 425°F (220°C). Grease a 1.5 litre 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 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 then pour heavy cream, sour cream and keep cooking until it forms bubbles on 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 cooked zucchini slices in row into the square baking dish See 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.


  • Store in the fridge in an airtight container for up to 4 days. Rewarm in a saucepan or in the microwave.
  • Freeze in single serve airtight container for easy single meal serve. Defrost in the fridge the day before and rewarm in the microwave or sauce pan.
Nutrition Facts
Keto zucchini casserole
Amount Per Serving (1 serve)
Calories 298.4 Calories from Fat 219
% Daily Value*
Fat 24.3g37%
Saturated Fat 14.6g91%
Cholesterol 76.6mg26%
Sodium 1216mg53%
Potassium 491.4mg14%
Carbohydrates 8.3g3%
Fiber 1.7g7%
Sugar 5.1g6%
Protein 13.4g27%
Vitamin A 1100.3IU22%
Vitamin C 28.4mg34%
Calcium 342.2mg34%
Iron 0.8mg4%
Net Carbs 6.6g
* Percent Daily Values are based on a 2000 calorie diet.

Keto zucchini casserole

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  1. 5 stars
    I absolutely have to leave a review- I followed this to the T and it is indescribable. A slice of this a day is going to change my life. It’s DELICIOUS. Thank you so much!!!

    • Thank you so much for the lovely feedback, I am so glad you enjoy this casserole too! Enjoy the keto recipes on the blog, XOXO Carine