Sheet Pan Squash Casserole Recipe | Easy & Cheesy

Let me tell you about last Thursday.

I opened my fridge and found three bags of summer squash staring back at me. My garden went absolutely wild this year, and I’d been putting off dealing with the overflow. I love squash, don’t get me wrong. But there’s only so many ways you can sauté it before you start feeling like you’re eating the same meal on repeat.

I wanted something with real presence. Something that could feed a crowd or give me leftovers for days. Something cheesy enough to make my kids stop asking what’s for dinner and just sit down and eat.

That’s when I remembered the old squash casserole my grandmother used to make. Rich, creamy, topped with those golden crackers that get all buttery and crisp. But here’s the thing—I didn’t want to mess with a deep dish. I wanted something I could slice into neat squares. Something that would get those crispy edges all over, not just around the rim.

So I grabbed my biggest sheet pan and decided to see what would happen.

And y’all. This turned out to be the best version I’ve ever made. We demolished half of it before it even cooled properly. My husband asked if I’d bring it to the next family cookout. That’s when you know you’ve got a keeper.

Here’s why this version just works

It’s ridiculously cheesy – We’re talking four and a half cups of cheddar here. No apologies. The cheese gets melty in the middle and a little crispy around the edges.

Every bite has that cracker crunch – Traditional casseroles have the topping, sure. But this one? You get buttery crackers on the bottom AND top. It’s like a cheesy squash sandwich situation, and I’m here for it.

It actually slices clean – Sheet pan style means you can cut perfect squares. Great for serving at potlucks or just portioning out leftovers.

It feeds a bunch – Eight generous servings from one pan. Perfect when you need to bring something to share or meal prep for the week.

Minimal cleanup – One sheet pan, one pot, one bowl. That’s it. No mountain of dishes afterward.

What goes into this beauty

You don’t need anything fancy or hard to find. Most of this is probably already sitting in your kitchen.

Summer squash (2 lbs) – Yellow squash is traditional, but zucchini works perfectly fine. I actually like mixing both. Slice them about ¼-inch thick so they cook evenly without turning to mush.

Yellow onion (½ medium) – Adds a subtle sweetness and depth. If you’re not an onion person, you can leave it out. But I’d encourage you to give it a try—it really rounds out the flavor.

Butter crackers (1 sleeve plus 1 cup crushed) – Ritz-style works best. The whole sleeve goes on the bottom, and you’ll crush another cup for the topping. If you’re gluten-free, use your favorite substitute crackers.

Cheddar cheese (4½ cups, divided) – I prefer sharp cheddar because it has more personality. But mild works if that’s what you like. Pre-shredded is fine, though freshly grated melts a bit better.

Sour cream (⅔ cup) – Adds tanginess and helps create that creamy texture. Greek yogurt can work in a pinch, though it won’t be quite as rich.

Mayonnaise (⅔ cup) – I know some folks are skeptical about mayo in casseroles. But trust me on this. It makes everything incredibly smooth and adds a subtle richness you can’t quite put your finger on.

Heavy whipping cream (¼ cup) – This is what makes it truly luscious. Half-and-half will work, but whole milk gets a little thin.

Seasonings – Garlic powder, black pepper, and salt. Nothing complicated. Just enough to wake everything up without overpowering the natural sweetness of the squash.

Eggs (2 large) – These help everything set up nicely so you can actually slice it instead of scooping it like soup.

Melted butter (1 tablespoon) – Mixed with the cracker topping for that golden, crispy finish.

Ingredients at a glance

Ingredient	Quantity	Notes
Summer squash (yellow or zucchini)	2 lbs	Sliced ¼-inch thick
Water	5 cups	For boiling squash
Yellow onion	½ medium	Chopped
Salt	1¾ teaspoons	Divided
Butter crackers	1 sleeve	For base layer
Cheddar cheese	4½ cups, divided	Grated, sharp preferred
Sour cream	⅔ cup	Full-fat recommended
Mayonnaise	⅔ cup	Regular, not light
Heavy whipping cream	¼ cup	For richness
Garlic powder	½ teaspoon	Or to taste
Black pepper	¼ teaspoon	Freshly ground preferred
Eggs	2 large	Beaten
Butter crackers	1 cup	Crushed for topping
Unsalted butter	1 tablespoon	Melted

Recipe Timing:
Prep Time: 10 minutes | Cook Time: 30 minutes | Total Time: 40 minutes
Servings: 8 | Difficulty: Easy

Let’s put this together – step by step

I’m going to walk you through this exactly how I make it. It’s honestly pretty straightforward, even if you’re not a confident cook.

Step 1: Get your oven ready

Preheat to 350°F. While that’s warming up, spray a 10×15-inch rimmed baking sheet with nonstick spray. Get into all those corners. Nothing worse than trying to scrape stuck cheese off a pan later.

Step 2: Cook the squash and onions

Grab a large pot and throw in your sliced squash, chopped onion, 5 cups of water, and 1 teaspoon of salt. Bring it to a boil over high heat, then reduce to a simmer. Let it cook for about 7 minutes until the squash is tender but not falling apart.

Drain everything really well in a colander. Let it sit for a minute or two so excess water can drip out. This step matters more than you’d think—too much water makes the casserole soggy.

Step 3: Build your cracker-cheese base

Take that sleeve of butter crackers and line the bottom of your prepared sheet pan. Lay them out like little tiles—don’t worry about gaps, just cover the bottom as best you can.

Sprinkle 3½ cups of shredded cheddar evenly over the crackers. Pop the whole thing in the oven for about 5 minutes. You’re not trying to brown anything here, just melt that cheese so it glues everything together. This creates the most amazing cheesy-crispy bottom layer.

Step 4: Mix up the creamy filling

While the cheese melts, grab a medium bowl. Whisk together your sour cream, mayo, heavy cream, garlic powder, black pepper, remaining ¾ teaspoon salt, and beaten eggs. It’ll look thick and rich—kind of like a fancy dressing. That’s exactly what you want.

Step 5: Layer the squash

Pull your pan from the oven. Spread the drained squash and onions evenly over that melted cheese-cracker base. Take your time with this. You want an even layer so everything cooks consistently.

Now pour your creamy egg mixture over the squash. Do this slowly and gently—if you dump it all in one spot, it’ll create a puddle instead of distributing evenly. I like to pour it in a spiral pattern, then use a spoon to nudge it into any dry spots.

Step 6: Add the finishing touches

Sprinkle the remaining 1 cup of cheddar cheese over everything. In a small bowl, mix your crushed crackers with the melted butter until the crumbs are coated. Scatter this mixture over the top of the casserole. Don’t pack it down—just let it sit there in a loose, craggy layer.

Step 7: Bake it to golden perfection

Slide the pan into your oven and bake for about 25 minutes. You’re looking for the center to be set (not jiggly) and the top to turn golden brown. Every oven’s a little different, so start checking around the 20-minute mark.

Step 8: The hardest part – waiting

I know it smells incredible. I know you want to dive right in. But you’ve got to let it rest for at least 20 minutes before cutting into it. This gives everything time to firm up so you get nice clean slices instead of a saucy mess.

Trust me on this. Walk away. Go set the table. Make a salad. Check your phone. Do whatever you need to do to give it time.

A few ways to make it your own

Once you’ve made this the regular way, here are some fun twists:

Add some meat – Crumbled cooked bacon or diced ham turns this into a heartier main dish. Stir it into the squash layer.

Kick up the heat – A pinch of cayenne pepper or some diced jalapeños in the cream mixture adds a nice subtle warmth.

Mix your cheeses – Try half cheddar and half Monterey Jack for an extra gooey texture. Or use Gruyere if you’re feeling fancy.

Herb it up – Fresh thyme or basil stirred into the cream mixture brings a bright, garden-fresh flavor.

Swap the topping – Crushed potato chips or panko breadcrumbs work great if you’re out of crackers. Toss them with butter the same way.

Make it lighter – Use reduced-fat cheese and swap sour cream for Greek yogurt. It won’t be quite as indulgent, but it’ll still be tasty.

Storing and reheating (because you’ll want seconds)

In the fridge: Cover tightly with foil or transfer to an airtight container. It’ll keep for up to 4 days. Honestly, I think the flavors meld even better on day two.

Reheating: For best results, warm individual portions in the oven at 300°F for about 10-12 minutes. The topping stays crispier that way. Microwave works too—just expect the crackers to soften a bit. About 1-2 minutes should do it.

Freezing: I’m going to be honest with you—I don’t recommend freezing this. The squash releases water when it thaws, and the whole thing gets watery and sad. The creamy filling separates. It’s just not great. Make what you’ll eat within a few days.

Common questions (because I get asked these a lot)

Can I use zucchini instead of yellow squash?

Absolutely. Zucchini works just as well, or you can do a mix of both. They cook the same way and have similar moisture content. Some people say yellow squash is a touch sweeter, but honestly, once it’s all cheesy and baked, you’d be hard-pressed to tell the difference.

Do I have to boil the squash first?

Yes, and here’s why. Raw squash releases a ton of water as it bakes. If you skip the pre-cooking, you’ll end up with a soupy mess instead of a casserole. Boiling it first gets rid of excess moisture and also ensures tender squash throughout.

Can I make this ahead of time?

You can prep it up to the point of baking, cover it tightly, and refrigerate for up to 24 hours. When you’re ready, let it sit at room temperature for 20 minutes, then bake as directed. You might need to add 5 extra minutes to the baking time since it’s starting cold.

What if I don’t have a sheet pan that size?

A 9×13-inch casserole dish works fine—it’ll just be a bit thicker. You might need to add 5-10 minutes to the baking time. The texture will be more like a traditional casserole, but it’ll still taste great.

My squash casserole turned out watery. What went wrong?

Usually this means the squash wasn’t drained well enough after boiling. Make sure you let it sit in the colander for a few minutes and even press it gently with paper towels if it seems really wet. Also, don’t skip the cooling time after baking—it needs that time to set up properly.

Can I skip the mayonnaise?

You could use all sour cream instead, but the texture won’t be quite as smooth. Mayo helps create that silky, creamy consistency. If you’re really opposed to mayo, try cream cheese instead—about ½ cup softened and beaten until smooth.

One last thing before you go

This sheet pan squash casserole has become one of those recipes I make without really thinking about it anymore. It’s the kind of dish that shows up at family gatherings, gets brought to neighbors who just had a baby, and appears on my own table on random weeknights when I need something comforting.

It’s not fancy. It’s not trendy. It’s just really, really good.

The kind of good that makes people ask for the recipe. The kind that disappears fast at potlucks. The kind where you eat one piece standing at the counter, then go back for another because nobody’s watching.

If you make this, I’d genuinely love to know how it turns out for you. Did you use the cheese I suggested or try something different? Did your family ask for seconds? Did you sneak a corner piece while it was cooling?

However it goes, I hope it becomes one of those recipes you make again and again. The ones that feel less like following instructions and more like coming home.