Zucchini is an amazing and versatile vegetable, and this humble veggie shines in this easy Zucchini Casserole with Sour Cream. This is a super easy casserole with cheese, onions, great seasoning, and zucchini. Perfect as a side dish or entree, this quick and easy casserole is perfect for zucchini lovers!

Zucchini Casserole with Sour Cream

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This Zucchini Casserole with Sour Cream is one of my favorites! It features sweet, tender-crisp zucchini, sweet onions, and a garlicky-cheesy-sour cream sauce with just the right amount of tang and flavor.

It’s also a great recipe to use zucchini from the garden if you have a bumper crop. Zucchini is available from just about any grocery store year-round, so don’t just wait for summer to make this easy casserole recipe.

Zucchini casserole with sour cream

You make it in an 8×8-inch baking dish, so there’s plenty to share, but not so much that you’ll be eating it for days.

cheesy baked casserole

I also love that the flavors in this zucchini casserole recipe are subtle enough that you can pair it with so many entrees.

When you’re looking for a cheesy vegetable casserole, give this Zucchini Casserole with Sour Cream a try – I’m sure you’ll love it!

a bite of casserole

Why I love this recipe

  • It’s easy to make and is loaded with tender-crisp zucchini.
  • This casserole is lower in carbs and is naturally gluten-free.
  • It pairs so nicely with so many dishes. See all my suggestions below!

zucchinis and ingredients

Gather these ingredients

  • Zucchini – You’ll need 4 large ones or 6 medium-sized.
  • Salt and cracked black pepper
  • Butter 
  • Sweet white onions – Use Vidalia or Spanish onions.
  • Garlic – Fresh cloves. 
  • Heavy whipping cream
  • Sour cream
  • Parmesan cheese – Shredded.
  • Mozzarella cheese – Shredded.
  • Gruyere cheese – Shredded.
  • Fresh basil – Chopped.
  •  

how to prepare zucchini

How to make the best Zucchini Casserole with Sour Cream

    1. Preheat your oven to 425-F and grease or spray an 8×8-inch baking dish with nonstick cooking spray. Set this aside.
    2. Slice the zucchini into ¼-inch thick slices and add them to a large bowl. Sprinkle the zucchini with 1 teaspoon of salt and toss gently. Set this aside for 20 minutes. Do not skip this step, or your casserole will be watery!
    3. Drain the zucchini slices by laying them on a clean kitchen towel or paper towel and pat them dry to remove the excess water. Do both sides.
    4. Melt 2 tablespoons of butter in a large saucepan over medium heat and saute the onions until soft. 
    5. Stir in the garlic and cook for an additional 30 seconds.
    6. Add the heavy whipping cream, sour cream, and ½ teaspoon of salt. Stir until hot and bubbly.
    7. Combine the Parmesan, mozzarella and gruyere cheeses in a medium bowl.
    8. Sprinkle ⅔ of the cheese mixture into the onion sauce and stir until thick and creamy.
    9. Layer the dried zucchini slices in rows in the square baking dish. You can overlap the rows.
    10. Pour the cheese and onion sauce over the top of the zucchini and spread evenly. Top the casserole with the remaining cheese.
    11. Bake at 425-F for about 20 minutes or until the zucchini is tender-crisp and the sauce is bubbly.
    12. Remove from the oven, top with freshly cracked black pepper and chopped basil.
  • Serve and enjoy!

spreading sauce on zucchini

Tips & substitutions

  • No heavy whipping cream? You can use half and half cream or extra sour cream.
  • Try to cut the zucchini all the same size for even cooking.
  • Insert a fork or a knife into the zucchini to test for doneness. You should feel some resistance. For best results, ensure the zucchini is tender-crisp.
  • If the top of your zucchini casserole starts to get too brown in the oven, cover it loosely with a sheet of foil.
  • You can use red onion or regular cooking onions, but they’ll have more bite to them than sweet onions.

shredded cheese on cream sauce

Serving suggestions

This easy Zucchini Casserole with Sour Cream pairs so nicely with so many other dishes if you want to serve it as a side. I love it with summery dishes like chicken kabobs or steaks on the grill. In the cooler months, I serve it with whole roasted chicken or a veggie-forward dish like Salmon with Wilted Greens

baked Zucchini Casserole

Storage

Store any leftovers in an airtight container in the fridge for 3-4 days. This casserole will not freeze well; it is best eaten fresh.

a serving of Zucchini Casserole with Sour Cream

Check out these awesome zucchini recipes while you’re here

Zucchini Casserole with Sour Cream
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Zucchini Casserole with Sour Cream

Savor the creamy delight of Zucchini Casserole with Sour Cream. A perfect blend of freshness and indulgence! Make in 8x8 baking dish.
Prep Time: 20 minutes
Cook Time: 20 minutes
Total Time: 40 minutes
Yield: 8
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Ingredients
 

  • 4 large zucchini, or 6 medium
  • 1 teaspoon salt
  • 2 Tbsp butter melted, divided
  • 1 ½ cup sliced sweet white onions
  • 3-4 garlic cloves, pressed
  • ½ cup heavy cream
  • ½ cup sour cream
  • ½ cup shredded Parmesan cheese, divided
  • ¾ cup Mozzarella cheese, grated & divided
  • ¾ cup Gruyere cheese, grated & divided
  • ½ teaspoon salt
  • Fresh basil, chopped
  • Fresh cracked black pepper

Instructions
 

  • Preheat oven to 425°F. Grease a square 8x8 baking dish with butter or cooking spray. Set aside.
  • Slice the zucchinis into 1/4 inch thick pieces, and place in a large bowl. Sprinkle 1 teaspoon of salt over the slices and toss gently with your hands. Set aside 20 minutes.
  • TIP: This step is important as it will extract the water from the zucchini to prevent a soggy, overly wet casserole. DO NOT SKIP!
  • Drain the zucchini slices by laying them on a kitchen towel or paper towel, patting them to remove as much excess water as you can (on both sides).
  • In a large saucepan, melt 2 Tbsp butter over medium heat and saute the onions until soft. Stir in garlic, heavy cream, sour cream, and 1/2 tsp salt and keep sauting until the mixture is hot and bubbly.
  • In a medium bowl, add all of the cheeses and mix together.
  • Sprinkle ⅔ of the grated cheeses into the onion mixture and stir until melted into a cheesy sauce.
  • Layer the zucchini slices in rows in the square baking dish. You will have about 4-6 rows of squash (depending on the size).
  • Pour the cheese and onion sauce over the top of the zucchini and spread evenly. Sprinkle the rest of the cheese over the zucchini.
  • Bake for 20 minutes; the sauce will be bubbly. Don't overbake; take a fork and make sure the zucchini is still slightly firm and remove from the oven. Sprinkle with fresh cracked black pepper and fresh chopped basil and serve!
  • TIP: If you don't have whipped cream on hand, you can use 1 cup of sour cream.
Cuisine: American
Course: Side Dish
Calories: 254kcal, Carbohydrates: 10g, Protein: 11g, Fat: 20g, Saturated Fat: 12g, Polyunsaturated Fat: 1g, Monounsaturated Fat: 5g, Trans Fat: 0.1g, Cholesterol: 60mg, Sodium: 745mg, Potassium: 532mg, Fiber: 2g, Sugar: 6g, Vitamin A: 962IU, Vitamin C: 32mg, Calcium: 293mg, Iron: 1mg
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Zucchini Casserole