When the garden starts producing more zucchini than you know what to do with, this is the recipe. Tender slices layered with freshly grated Swiss and mild cheddar, bathed in a silky brie cream sauce, and broiled until the top caramelizes into something you’ll want to photograph before anyone touches it. Gluten free, no breadcrumbs, and genuinely hard to stop eating.

Overhead view of cheesy zucchini casserole with melted Swiss and cheddar cheese in a red Staub baking dish

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Every summer, the zucchini situation gets a little out of hand. The garden produces three, then eight, then suddenly you’re finding them tucked into bags on your doorstep from neighbors who have given up. I am not complaining – I actually love this problem, because it gives me a reason to make this cheesy zucchini casserole on repeat until September.

This is not the watery, limp baked zucchini you’ve had at potlucks. It’s something closer to a gratin – tender slices layered with freshly grated Swiss and mild Cheddar, bathed in a silky brie cream sauce, then broiled until the top goes deeply golden and slightly caramelized. No breadcrumbs, no thickeners, nothing unnecessary. Just vegetables, cheese, and a technique that makes it feel like you put in far more effort than you actually did.

I made it on a day with no particular occasion in mind, and it disappeared before I got to photograph the second serving. That’s when I knew it needed to be on the blog!

Why You’ll Love This Cheesy Zucchini Casserole

Summer in my kitchen tends to look like this – something warm and cheesy in the oven, something bright and fresh on the side. If you haven’t tried my peach bruschetta with ricotta and honey yet, it makes a stunning starter while this casserole bakes.

No watery texture – the salting and draining step before baking makes all the difference, and I’ll walk you through it properly
No breadcrumbs – which means it’s naturally gluten-free, and the cheese on top does all the textural work
The broiled crust – five minutes under the broiler transforms a good casserole into a great one
A cheese combination that actually works – Swiss for nuttiness and melt, mild Cheddar for golden color and gentle sharpness; both freshly grated
Simple enough for a weeknight, impressive enough for guests – the kind of side dish that makes a regular dinner feel considered

Cheesy zucchini casserole with a golden broiled cheese crust in a white ceramic baking dish on a wood cutting board

Ingredients and What They Do

Zucchini – three medium ones, sliced into ¼-inch rounds. Medium is the key word here. Oversized zucchini have more seeds and hold more water, which makes the watery-casserole problem worse even when you drain them. When you’re at the market, reach for firm, smaller squash with bright skin.

Swiss and mild cheddar cheese – two cups total, grated fresh, split 50/50. This is the version I made, and it’s the one I’ll make again. Swiss brings a subtle nutty quality and melts into beautiful, silky pools. Mild cheddar gives the casserole that warm golden color when broiled and a gentle sharpness that balances the richness of the cream sauce. The most important part: grate it yourself. Pre-shredded cheese is coated with anti-caking agents that prevent it from melting as smoothly. Five extra minutes at the grater is genuinely worth it.

Brie – three ounces, rind removed. This is the secret of the cream sauce. Brie melts down into something silky and slightly tangy, thickening the sauce without flour or starch. It’s what makes this casserole feel French-adjacent – a little bistro-like without asking anything difficult of you. If brie isn’t your thing or you don’t have it, cream cheese works well as a substitute and gives a milder, more neutral sauce. Brie is also one of my favorite cheeses for salads – if you’ve never tried it that way, my fresh fig, arugula and brie salad with vanilla-shallot vinaigrette is worth bookmarking for fig season.

Heavy cream – a third of a cup. It loosens the sauce just enough to pour it over the zucchini evenly. Don’t swap this for milk or half-and-half without reducing the quantity, or the sauce will be too thin.

Butter and garlic – one tablespoon of unsalted butter and two cloves of minced garlic. They go straight into the sauce and give it depth without complicating anything.

Italian seasoning – half a tablespoon, scattered over the top before baking. It blooms in the heat and gives the golden top a herby, fragrant finish.

Sea salt – used in two places: to draw moisture from the zucchini before baking, and optionally in the cream sauce. Because the zucchini is salted in step one, taste the sauce before adding more.

The Technique That Makes It Work: How to Keep Zucchini Casserole from Getting Watery

Zucchini is mostly water. When you bake it without preparation, that water releases into the dish and pools at the bottom, diluting the sauce and leaving you with something soupy rather than creamy. Every step in this recipe is designed to prevent that.

Salt and drain the zucchini first. Toss the sliced rounds with sea salt, place them in a colander over the sink, and walk away for 50 minutes. The salt pulls out a significant amount of moisture before the zucchini ever sees the oven. You’ll be surprised how much liquid collects underneath.

Pat them thoroughly dry. Draining removes moisture from the inside, but there’s still surface water. Press the slices firmly with paper towels – use several layers and take your time. The drier they are going in, the creamier the result coming out.

Use a medium casserole dish, not a large one. A smaller dish keeps the sauce concentrated and coating the zucchini, rather than spreading thin across the pan floor. I use a medium baking dish – roughly equivalent to a 9×9 or a 2-quart dish. If you only have a 9×13, scale the recipe up by about 1.5x.

Use the broiler at the end. Those extra five minutes under heat aren’t just for aesthetics. They also help evaporate any final surface moisture and tighten up the sauce, giving you a set, sliceable casserole rather than a loose one.

How to Make This Cheesy Zucchini Casserole – Step by Step

Step 1: Salt and Drain the Zucchini

Slice the zucchini into ¼-inch rounds and toss them with the sea salt. Transfer to a colander set over the sink and let them sit for 50 minutes. After draining, pat the slices firmly dry with paper towels. Don’t rush this step – it’s the foundation of a non-watery casserole.

Step 2: Preheat and Prep

Set your oven to 400°F (204°C). While it heats, grate your cheese if you haven’t already.

Step 3: Layer the Zucchini and Cheese

In your medium casserole dish, arrange the zucchini slices in overlapping rows. As you build up the layers, sprinkle cheese in between – you’re using about half the total (1 cup) during this assembly. The slices should overlap generously; they’ll shrink slightly as they cook. Season with a little black pepper. Hold off on adding more salt here.

Step 4: Make the Brie Cream Sauce

In a small saucepan over medium-low heat, combine the brie, heavy cream, butter, Italian seasoning and minced garlic. Stir gently and frequently as the brie melts. It will look chunky at first, then smooth out into a pourable sauce – this takes about 3 to 5 minutes. Don’t rush it with high heat; you want a smooth emulsion, not a broken sauce. Taste it now and add a pinch of salt if it needs it. Pour the sauce evenly over the layered zucchini.

Step 5: Top with Cheese

Scatter the remaining 1 cup of grated cheese over the top.

Step 6: Bake

Place in the preheated oven and bake for 20 to 25 minutes, until the zucchini is fork-tender and the cheese is fully melted and starting to turn golden at the edges.

Step 7: Broil for the Crust

Switch the oven to broil. Keep the casserole on the same rack and broil for 5 minutes, watching closely the entire time. You’re looking for the top to turn deeply golden and develop some caramelized, slightly darker spots – that contrast between the crispy cheese crust and the creamy interior underneath is the whole point. Pull it out the moment it looks right; the difference between perfect and burnt under a broiler is genuinely about 60 seconds.

Let the casserole rest for 5 minutes before serving.

Raw zucchini rounds layered in overlapping rows with freshly grated Swiss and cheddar cheese in a red Staub casserole dish

Brie cream sauce poured over overlapping zucchini slices and shredded cheddar and Swiss cheese in a Staub baking dish

Expert Tips

On the cheese: The Swiss and cheddar combination was my personal adaptation, and it’s become my preferred version of this dish. Swiss melts quietly and adds a European, slightly nutty depth. Mild cheddar brings color and that familiar sharpness without overwhelming the brie sauce. You can also use Gruyère in place of Swiss if you want a more pronounced nuttiness.

On making the sauce smooth: Make sure all the rind is removed from the brie – even small pieces prevent it from melting uniformly. Use low to medium-low heat and keep stirring. If the sauce looks grainy, give it another minute and keep stirring; it will come together.

On the broiler: Leave the oven door slightly open and stay in the kitchen. Some broilers run hotter than others, and five minutes is a guideline, not a guarantee. Watch for the color.

Make ahead: You can assemble the casserole through step 5 and refrigerate it, covered, for up to a day before baking. Note that the longer the assembled dish sits, the more moisture the zucchini can release, so baking fresh is always ideal.

Storage: Leftovers keep in an airtight container in the refrigerator for up to 3 days. Reheat in a 350°F oven for best texture, or microwave individual portions. I don’t recommend freezing – cream sauces tend to separate when thawed.

What to Serve with This Zucchini Casserole

This is a side dish that plays well with almost anything and elevates a simple protein into a real meal.

Grilled or roasted chicken – the creaminess of the casserole pairs beautifully with simply seasoned chicken
Pan-seared salmon or halibut – the richness of the cheese sauce complements fish without competing. This is a side dish that plays well with almost anything, and it pairs especially well with fish. If you’re building a full summer dinner, try it alongside my cheesy couscous with salmon – or keep things light and let the casserole take the lead.
Pork chops or tenderloin – a classic pairing; the nuttiness of the Swiss echoes nicely with pork
As a vegetarian main – serve with a simple arugula or herb salad and crusty bread; it’s substantial enough to stand on its own. If you want something bright and fresh to balance the richness of the cheese sauce, my lemon-dill orzo salad with arugula and feta is exactly the right contrast – it comes together in under 30 minutes and works beautifully alongside a warm baked dish like this.

Frequently Asked Questions

How do I keep zucchini casserole from getting watery? Salt the sliced zucchini, let it drain in a colander for at least 50 minutes, then pat very dry with paper towels before layering. Using a medium-sized dish rather than a large one also helps keep the sauce concentrated rather than spreading thin. Broiling at the end evaporates any residual surface moisture.

Can I use yellow squash instead of zucchini? Yes – yellow summer squash has a nearly identical texture and moisture content. A mix of yellow squash and zucchini looks beautiful in the dish and tastes just as good.

Can I substitute the brie? Cream cheese is the best substitute and gives a milder, more neutral cream sauce. Use the same 3-ounce quantity.

Is this zucchini casserole gluten-free? Yes. There are no breadcrumbs or thickeners in this recipe. All the structure comes from the cheese and the cream sauce.

Can I make it ahead of time? You can assemble it up to a day in advance and refrigerate before baking. That said, the zucchini will continue releasing some moisture as it sits, so baking fresh gives the best result.

Why should I grate my own cheese? Pre-shredded cheese contains anti-caking coatings (often potato starch or cellulose) that affect how it melts. Freshly grated cheese melts smoother and more evenly, which matters both in the layers and on the top crust.

How long does this zucchini casserole keep? Up to 3 days in the refrigerator in an airtight container. It gets slightly softer on reheating but is still delicious. Do not freeze.

If you’re building a summer spread around this casserole, the goat cheese and fig stack with prosciutto and hot honeymakes a perfect starter – cheesy, elegant, and ready in minutes.