Baked in the oven or smoked on the grill, this hearty, cheesy zucchini casserole is a must try! It’s the perfect side dish to go with your next meal or enjoyed as a meal by itself.
I have always been a big fan of casseroles. Growing up, my mom had a rotating list of casseroles to take to any gathering. In the summertime, zucchini casserole was always at the top of that list. We usually had an abundance of zucchini from the garden and sometimes had to get creative with ways to use it all up. I wasn’t a big fan of this as a kid, but I can’t get enough of it as an adult.
The one thing you should know about zucchini is that it’s a vegetable that naturally holds a lot of water. Liquid will be released when the zucchini is baking, which we do not want in our casserole. To avoid having a mushy or watery dish, we use a method for releasing moisture in the zucchini before mixing it with the other ingredients. Be sure to follow all of our tips for this recipe and enjoy the delicious results.
Ingredients
As with most casseroles, this one uses many pantry staples you likely already have on hand. Here is everything you will need and what it adds to the dish:
- Zucchini – 2 pounds which is usually about 4-5 medium-sized zucchini.
- Panko Breadcrumbs – provides a crunchy topping.
- Butter – I like to use unsalted butter to be able to control the amount of salt in the casserole.
- Yellow Onion – Adds a savory flavor to the dish.
- Olive oil – Used for cooking the onions.
- Eggs – Help to bind the cheese and zucchini together when baking.
- Minced Garlic – Adds depth to the seasoning.
- All-Purpose Flour – Used as a base for making the sauce to help it thicken.
- Heavy Whipping Cream – Provides a remarkable consistency to the creamy cheese sauce.
- Cream Cheese – Makes the dish hearty without being overly heavy.
- Cheddar Cheese and Grated Parmesan – Both types of cheese are divided and whisked into the sauce and used to layer the casserole.
- Fine Sea Salt and Ground Black Pepper – These simple ingredients are used to season the dish.
How To Make Zucchini Casserole
Most anything cooked in the oven can also be done on the grill. I love the slightly smoky flavor achieved by doing this recipe on the grill, but I will leave the cooking method up to you. To begin, heat your grill (or oven) to 400°F and grease a cast-iron skillet with a thin layer of oil and set aside. Then, melt 2 tablespoons of butter and mix with the breadcrumbs. This will be used for the topping later on.
How To Prepare The Zucchini
Because zucchini has so much water in it, there are a few steps needed to get it ready for the casserole. First, you will need to slice it into ¼” circles and place it into a bowl. I like to use a mandoline to keep them consistent but a knife works great too.
To draw out moisture and prevent the liquid from being released into your casserole, start by sprinkling 1 teaspoon of salt on top of the zucchini and toss it with your hands. Then, place the zucchini slices onto a paper towel lined cookie sheet, in an even layer and cover it with another layer of paper towels.
Place your cast iron skillet on top of one side of the pan for 15 minutes. After 15 minutes, place the skillet on the other side of the cookie sheet for an additional 15 minutes.
How To Prepare The Cheese Sauce
While the zucchini slices release their liquid, heat the olive oil in a frying pan with high sides (NOT the cast iron) over medium-low heat and add the onions. Cook for about 10 minutes, stirring often, until the onions are golden brown.
To the cooked onions, add the remaining 2 tablespoons of butter, black pepper, 1 teaspoon
salt, and minced garlic. Cook for 2-3 minutes until the butter is melted and the garlic becomes fragrant. Be careful not to burn the garlic.
Add the flour to the pan and constantly mix until the onions are fully coated in flour, and it dissolves, about 2 minutes. Over medium heat, whisk in ½ cup of the heavy cream at a time, whisking well in between each addition. Once the sauce begins to thicken (which will happen nearly immediately), turn off the heat.
Remove the pan from the heat and vigorously whisk in the cream cheese, beaten eggs, half of the cheddar cheese, and half of the parmesan. Whisk for 2 minutes to ensure the sauce is emulsified and all the cheeses are melted. Before adding the zucchini, blot it one last time with another paper towel to remove any excess moisture. Transfer the zucchini to the pot of cream sauce and mix together until the slices are fully coated.
How To Assemble And Bake The Casserole
Spoon half of the cheesy zucchini mixture (roughly 3 cups) into the cast iron skillet and spread into an even layer. Sprinkle with ¼ cup shredded cheddar cheese and ¼ cup grated parmesan. Then, layer the remaining zucchini mixture on top. Sprinkle the remaining shredded cheddar cheese and grated parmesan on top.
Tent the skillet with aluminum foil and place it onto the preheated grill over indirect heat for 30 minutes. Then remove the foil and sprinkle the prepared breadcrumbs over top and bake for an additional 25 minutes.
If baking in the oven follow the same bake times as above. The only change would be that I recommend placing the cast iron skillet on a baking sheet just in case any of the cheese oozes over the side. This will also help prevent any burnt on messes inside the oven.
Once the bread crumbs are all golden brown, place the pan onto a wire cooling rack. Allow to cool for at least 20 minutes before serving to allow any excess liquid to thicken and set. Alternatively, cool for 1-2 hours before storing in the refrigerator.
What To Serve With Zucchini Casserole
While this dish can be served by itself as a meatless option, it also makes a great side dish with so many different meals. Try some of our other grilled recipes to pair with this casserole.
Zucchini Casserole
Ingredients
- 4 tablespoons unsalted butter divided
- ½ cup panko breadcrumbs
- 2 pounds zucchini about 4-5 medium zucchini
- 2 teaspoons salt divided
- 2 tablespoons olive oil
- 1 medium yellow onion peeled and diced small
- ¼ teaspoon ground black pepper
- 6 cloves garlic minced
- ¼ cup all-purpose flour
- 1 ½ cup heavy whipping cream
- ½ cup cream cheese 4 ounces
- 2 large eggs at room temperature, lightly beaten
- 8 ounces cheddar cheese shredded
- 4 ounces parmesean cheese finely grated; divided
Instructions
- Preheat the oven or grill to 400°F. Grease a cast-iron skillet with a thin layer of oil and set aside.
- Melt 2 tbsp butter in a medium microwave-safe bowl for 20-second intervals until fully melted. Then, mix in the panko breadcrumbs. Set aside for later.
- Slice the zucchini into ¼” circles and place into a bowl. Sprinkle 1 teaspoon of salt on top and toss with your hands. Place the zucchini slices onto a paper towel-lined cookie sheet in a mostly even layer, and cover with a paper towel as well. Place your cast iron skillet on top of one side of the pan to press out the liquid and keep it there for 15 minutes. After 15 minutes, place the skillet on the other side of the cookie sheet to press liquid out of the other half of the zucchini slices.
- While the zucchinis release their liquid, heat the olive oil in a frying pan with high sides (NOT the cast iron skillet) over medium-low heat and add the onions. Cook for about 10 minutes, stirring often, until the onions are golden brown.
- To the cooked onions, add the remaining 2 tbsp butter, black pepper, 1 teaspoon salt, and minced garlic. Cook for 2-3 minutes until the butter is melted and the garlic becomes fragrant. Be careful not to burn the garlic.
- Add the flour to the pot and constantly mix until the onions are fully coated in flour and it dissolves for about 2 minutes.
- Over medium heat, whisk in ½ cup of the heavy cream at a time, whisking well in between each addition. Once the sauce begins to thicken (which will happen nearly immediately), turn off the heat.
- Remove the pan from the heat and vigorously whisk in the cream cheese, beaten eggs, half of the cheddar cheese, and half of the parmesan. Whisk for a full 2 minutes to ensure the sauce is emulsified and all cheeses are melted.
- Blot the zucchini one last time with a new piece of paper towel to remove any excess moisture. Transfer the zucchini to the pot of cream sauce and mix together until the zucchini is fully coated.
- Spoon half of the cheesy zucchini mixture (about 3 cups) into the cast iron skillet and spread it into an even layer. Sprinkle with ¼ cup of shredded cheddar cheese and ¼ cup of grated parmesan cheese. Then, layer the remaining zucchini mixture on top. Sprinkle the remaining ¼ cup of shredded cheddar cheese and ¼ cup grated parmesan cheese on top.
- Tent the skillet with aluminum foil and place it onto a cookie sheet in case any cheese oozes out. Place over indirect heat on the grill (or bake on the center rack of the oven) for 30 minutes. Remove the foil and sprinkle with the buttery breadcrumbs. Bake for an additional 25 minutes.
- Once ready, place the pan onto a wire cooling rack. Allow to cool for at least 20 minutes before serving to allow any excess liquid to thicken and set. Alternatively, cool for 1-2 hours before storing in the refrigerator.
Notes
- Allow to cool fully before storing in the refrigerator. This will help any extra condensation from forming and making the casserole soggy.
- If baking in the oven I recommend placing the skillet on top of a baking sheet to prevent any cheese from oozing over and making a mess.
- Any left overs can be stored in an air tight container in the refrigerator for up to 3 days.