This zucchini casserole is low-carb side dish made with layered sliced zucchini and a creamy parmesan cheese sauce. A delicious baked zucchini gratin recipe comes together in under 40 minutes, and it’s gluten-free and keto-friendly.
Made with just a handful of ingredients, this zucchini bake is a perfect side dish for a busy weeknight dinner. It’s loved even by the picky eaters that normally hate zucchini. The zucchini is perfectly cooked (fork tender with a slight crunch), and it’s covered in the creamiest garlic cheese sauce. It’s a 5 STARS recipe, for sure!
Zucchinis are one of my favorite vegetables – EVER! They are super versatile and can be cooked in various ways:
- Delicious roasted or grilled
- Fantastic in frittatas
- Tasty raw in salads
- Great pasta replacement as zoodles
- It can be stuffed with anything
- A fabulous addition to soups
- It can be added to desserts to keep them moist – try my double chocolate keto zucchini pound cake.
And these are just some of the ways to cook zucchini that just crossed my mind. Zucchini is low in calories and carbs, making it the perfect vegetable for any lifestyle.
If you’re still looking for delicious zucchini recipes, I have more like Zucchini Slice, Zucchini Pizza Bites, Zucchini Lasagna, or Parmesan Baked Zucchini Fries.
Watch this quick step-by-step video on how to make this delicious zucchini casserole!
Why This Zucchini Casserole Recipe Works
- The best way to use up those summer zucchini
- Super cheesy and delicious
- Easy to make with basic ingredients
- Just 10 minutes of hands-on prep.
- Completely gluten-free and grain-free
Ingredients For Zucchini Casserole
Here’s a quick overview of the ingredients needed to make this baked cheesy zucchini casserole recipe. As usual, the complete list of ingredients and instructions can be found in the recipe card below.
- Zucchini – choose firm, unblemished zucchini with smooth skin. I used about 3 medium zucchini as they are less watery and have less seeds.
- Butter – I used unsalted one, but if you choose to use salted butter, you have to reduce the amount of salt you use.
- Heavy Cream – Makes the cheese sauce creamy and amazing.
- Cheese – Parmesan and Mozzarella Cheese
- Onion and Garlic – add great texture and flavor.
- Fresh herbs such – Parsley, Chives, or Thyme
- Seasonings – I use a basic combo of salt and pepper.
TIP: Add any leftover chicken, ground beef, or turkey to the casserole for more flavor.
How To Make Baked Zucchini Casserole
I always seem to have leftover zucchini, so the best way to use them up is to make this cheesy baked zucchini casserole recipe in just a few easy steps:
Prepare the Zucchini
Remove the ends of the zucchini and slice it into 1/4 inch thick rounds using a sharp knife or a mandoline. Sprinkle the zucchini with salat and place them on a few paper towels to remove as much moisture as possible.
Make the Sauce
Melt the butter in an oven-safe pan over medium heat. Then cook the onions and garlic for a few minutes until fragrant.
Stir in the whipped cream and simmer for approximately 2 minutes, or until it thickens. Then, you can add the parmesan cheese.
Assemble the Zucchini Casserole
Arrange the zucchini and mozzarella slices in the baking dish and pour over the cheese sauce. Sprinkle shredded mozzarella cheese on top.
Baking the Casserole
Bake the casserole in the preheated oven for 25 minutes, or until the zucchini is fork tender and the cheese is golden brown on top.
Tips For Making The Best Zucchini Casserole
- After slicing the zucchini, sprinkle some salt and place the slices on a flat surface. Set aside for 30 minutes and pat dry using paper towels to remove as much moisture as possible.
- I used parmesan cheese and mozzarella, but you can also use cheddar cheese.
- If the zucchini casserole looks too watery, reduce the oven temperature to 350°F and cook for 10 to 20 more minutes.
- For a crunchy topping, I recommended adding some crushed pork rinds or panko.
- Let the zucchini gratin rest for 5-10 minutes before serving. This will allow the cheese to set and make it easier to serve.
- Garnish with fresh parsley or basil. Some red pepper flakes add the perfect spicy kick.
- Serve as a side dish for chicken or fish or a main dish with a fresh salad.
What Kind Of Cheese Can I Use
I prefer to use a mix of Parmesan and mozzarella cheese. You may use whatever type of cheese you love. It’s all up to you. I buy blocks of cheese from the store and grate them myself. Preservatives and cornstarch are commonly included in pre-shredded cheese, and it doesn’t melt well.
How To Store This Zucchini Gratin
- Fridge – Store covered in the fridge for up to 4 days. When ready to enjoy, reheat at 350F or in the microwave until warmed through.
- Freezer – I don’t recommend freezing the leftovers because both zucchini and the cream sauce don’t thaw correctly, and the texture is unpleasant.
Zucchini Casserole Variations
I want to share a few ideas with you that you might want to try. Naturally, you may eat it exactly as I wrote it, but if you prefer to branch out, here are some suggestions.
- Tomatoes – Sun-dried tomatoes or fresh tomatoes can also be used. Chop tomatoes up or mix in some cherry tomatoes. Both have a strong taste and will complement the other ingredients in the casserole.
- Bacon – Some cooked, crumbled bacon can be added to the zucchini casserole mixture.
- Hot Sauce – if you prefer some extra heat, mix some hot sauce into the cheesy sauce.
- Use different cheeses and herbs for more depth of flavor and complexity.
Is it Necessary to Pre-Cook the Zucchini?
In this recipe, there’s no need to cook the zucchini beforehand. Instead, please place it in the pan uncooked, then cover it with the cheese sauce and bake it. In approximately 20-30 minutes, it’s ready to be served with your favorite mains.
Can I Make This In A Slow Cooker?
Yes, you can make this simple zucchini casserole in a slow cooker. Here is what you have to do:
- Prepare the zucchini, just like I mentioned earlier.
- Place the zucchini into the slow cooker. Make the cheese sauce on the stove according to the recipe’s directions.
- Cook for 3-4 hours on low.
Is Zucchini Keto-Friendly?
Sure, zucchini is keto-friendly since it is low in both calories and carbohydrates. This means you may include this vegetable in your ketogenic diet.
According to the USDA database, 1 cup of sliced zucchini (113 grams) has only 2.4 grams of net carbohydrates and 19 calories.
Feel free to serve this zucchini casserole with any of your favorite mains. My favorites include:
- Chicken Parmesan
- Garlic Herb Butter Roasted Turkey Breast
- Baked Chicken Thighs
- Air Fryer Naked Chicken Tenders
- Grilled Chicken Kabobs
Best Zucchini Casserole – Super Creamy and Cheesy
- 2-3 medium zucchini sliced thin & cut in half circles
- ½ cup parmesan cheese freshly grated
- 3 tbsp butter
- 1 medium onion sliced
- 3 garlic cloves minced
- ½ cup heavy cream
- ¼ cup low sodium beef broth or water
- 1 cup mozzarella cheese shredded
- ½ cup mozzarella slices optional
- ½ tsp of salt or more to taste
- ½ tbsp pepper or more to taste
- Preheat oven to 400F. Coat a 2-quart casserole dish with non-stick cooking spray, and set aside.
- In a large oven-proof skillet, melt the butter. Cook the onions until translucent and fragrant.
- Add in the minced garlic and cook for about 1 minute, stirring constantly.
- Add in the broth, salt, pepper, and pour the heavy cream. Stir to combine and bring to a simmer.
- Reduce the heat and add in the parmesan cheese. Simmer for 2-3 minutes until it starts to thicken.
- Arrange the sliced zucchini in the bottom of a casserole dish, overlapping each other. Place mozzarella slices between zucchini slices, as shown in the video.
- Evenly pour the cheese on top of the zucchini, then sprinkle the mozzarella cheese.
- Bake for 25-30 minutes or until the cheese on top starts to brown, and the zucchini are fork tender.
- Garnish with fresh parsley or chives. Enjoy!
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.
The full recipe is in the recipe card below. Readers that love this aslo made these recipes:
This sauce is delicious! I made it with zoodles instead of the slices but it’s all the same! (; We loved it, and it was so easy. Thank you!