Creamy Summer Squash Casserole (No Watery Mess)

Summer squash casserole is the kind of side dish that shows up at every potluck for good reason. It’s rich, cheesy, and topped with buttery cracker crumbs that everyone fights over.

Most versions end up a little watery, but this one holds together beautifully. A quick salting step pulls out extra moisture, so you get a creamy, golden-baked scoop every time.

Why This One Stays in the Rotation

I lean on this recipe all summer when the garden gives me more squash than I can keep up with. The trick is salting the squash before it ever hits the casserole dish.

That step draws out the water that would otherwise make the whole thing soupy. What’s left is tender squash folded into a sharp cheddar and sour cream sauce that bakes up rich, not runny.

The top stays crisp because the buttery cracker crumbs go on right before the pan slides into the oven. It’s the best version of the church cookbook classic, and I mean that.

Ingredients

• 2 lbs yellow squash or zucchini: a mix of both works great, yellow holds a bit less water
• 1 medium yellow onion: diced small
• 1 tsp fine sea salt: for drawing moisture from the squash
• 2 tbsp unsalted butter: plus more for greasing the dish
• 2 tbsp all-purpose flour
• 1 cup whole milk: 2% is fine, but whole keeps the sauce silkier
• 1 cup shredded sharp cheddar cheese: freshly grated melts better than the bagged stuff
• 1/2 cup sour cream: full-fat gives the creamiest texture
• 1 large egg: lightly beaten
• 1/2 tsp black pepper
• 1 cup crushed buttery round crackers: like Ritz, about 1 sleeve
• 2 tbsp unsalted butter, melted: for the topping

Variations

• Make it with all zucchini: the salting step is even more important since zucchini holds more water. Squeeze it thoroughly before it hits the sauce.
• Swap the crackers for panko: you’ll get a lighter, crunchier top. Toss the panko with the melted butter and a pinch of salt.
• Add a hit of heat: stir a pinch of cayenne into the cheese sauce or scatter pickled jalapeños over the top before the crumbs.
• Go gluten-free: use a 1-to-1 gluten-free flour blend and gluten-free buttery crackers. The sauce thickens the same.
• Try Greek yogurt: plain full-fat Greek yogurt stands in for the sour cream nicely, just keep the same ½ cup measure.

Creamy Chicken Divan Casserole is next on our list if this casserole is your kind of dinner.

How to Make Creamy Summer Squash Casserole

Step 1: Salt and Drain the Squash

Trim the ends off the squash and slice them into ¼-inch thick half-moons. Toss the slices with the 1 tsp salt in a large colander, then let them sit in the sink or over a bowl for 30 minutes. You want the salt to pull as much liquid out as possible.

After half an hour, give the squash a quick rinse under cold water to wash off the extra salt. Then grab handfuls and press them firmly between paper towels or a clean kitchen towel. The squash should feel noticeably drier when you’re done.

Step 2: Whisk the Cheese Sauce

While the squash drains, melt the 2 tbsp butter in a medium saucepan over medium heat. Toss in the diced onion and cook, stirring now and then, until it turns soft and translucent, about 4 minutes. Sprinkle in the 2 tbsp flour and stir constantly for 1 minute to cook out the raw flour taste.

Slowly pour in the 1 cup whole milk while whisking. Keep whisking until the sauce comes together and thickens enough to coat the back of a spoon, 3 to 4 minutes. Pull the pan off the heat, then stir in the 1 cup shredded cheddar, ½ cup sour cream, the beaten egg, and the black pepper. The sauce will be smooth and glossy.

Step 3: Fold the Squash into the Sauce

Add the drained squash to the cheese sauce and use a spatula to fold everything together until every piece is coated. Don’t worry if the mixture looks a little soupy at this point. The egg sets up in the oven and turns it into a sliceable casserole.

Scrape the whole thing into a buttered 8-inch square baking dish (a 2-quart dish works too) and spread it into an even layer. Set the dish aside while you mix the topping.

Step 4: Top and Bake the Casserole

Preheat the oven to 350°F (175°C). In a small bowl, toss the 1 cup crushed crackers with the 2 tbsp melted butter until everything is moistened. Scatter the crumbs evenly over the squash mixture.

Slide the dish into the oven and bake until the top is deep golden brown and the edges are bubbling hard, 30 to 35 minutes. The center should be set and not jiggle much when you give the dish a gentle shake.

Step 5: Rest and Serve the Casserole

Move the dish to a cooling rack and let it rest for at least 10 minutes. Those minutes let the casserole firm up so you can get clean, creamy scoops instead of a sloppy mess.

Serve it warm right from the dish. A little shower of fresh chives or parsley on top makes it look as good as it tastes.

A Few Notes Before You Start

• Smaller squash have fewer seeds and less water, so they need less squeezing. If you’re grabbing them at the farmers market, pick the ones that feel firm and heavy for their size.
• If the cracker topping starts browning too fast, tent the dish loosely with a piece of foil and let it finish baking. The crumbs will still crisp up, just a little slower.
• You can build the casserole without the topping and refrigerate it overnight. The next day, bring it to room temperature while the oven preheats, add the crumbs, and bake as directed.
• Leftover cooked ham or crumbled bacon folded into the squash mixture adds a smoky, salty bite that works really well with the cheese sauce.

Bake times shift a bit depending on your dish:

Storing and Reheating Leftovers

• Refrigerate: Tuck any leftovers into an airtight container and keep them in the fridge for up to 4 days.
• Reheating: A 350°F oven for 10 to 15 minutes brings the topping back to life. The microwave works in a pinch, but the crumbs will soften.

What Goes Well With Summer Squash Casserole

This casserole fits right next to anything coming off the grill or smoker. Smoked chicken are great matches because the creamy, cheesy squash contrasts with the smoky meat without competing. For a weeknight dinner, it’s just as good beside a classic meatloaf.

Frequently Asked Questions

Can I use zucchini instead of yellow squash?

Yes, you can use all zucchini or a mix. Zucchini holds more water, so be extra thorough with the salting step and squeeze it firmly dry before folding it into the sauce.

Can I swap in cream of mushroom soup for the white sauce?

You can. Replace the butter, flour, and milk with one 10.5-ounce can of condensed cream of mushroom soup. Stir in the cheese, sour cream, and egg as directed. The texture will be a little looser but still good.

My casserole turned out dry. What went wrong?

You might have wrung out the squash too aggressively or baked it longer than needed. The squash should still feel slightly moist after draining, not bone-dry.

Why did my cracker topping get soggy?

Sogginess happens when the crumbs sit on the casserole too long before baking or if the dish is covered with foil the whole time. Sprinkle the topping on right before the pan goes in the oven, and only tent with foil if it’s browning too fast.

Creamy Summer Squash Casserole Recipe

Print Recipe Pin Recipe

Prep Time 15 minutes mins

Cook Time 35 minutes mins

Total Time 50 minutes mins

Servings: 6 servings

Calories: 290

Ingredients Method Notes

Ingredients

  

• 2 lbs yellow squash or zucchini
• 1 medium yellow onion
• 1 tsp fine sea salt
• 2 tbsp unsalted butter
• 2 tbsp all-purpose flour
• 1 cup whole milk
• 1 cup shredded sharp cheddar cheese
• 1/2 cup sour cream
• 1 large egg
• 1/2 tsp black pepper
• 1 cup crushed buttery round crackers
• 2 tbsp unsalted butter, melted

Method

 

1. Slice squash into 1/4-inch half-moons. Toss with salt in a colander and let drain 30 minutes. Rinse, press dry with paper towels.
2. In a saucepan over medium heat, melt 2 tbsp butter. Cook onion until soft, about 4 minutes. Stir in flour and cook 1 minute. Whisk in milk, cook until thickened, 3 to 4 minutes. Off heat, mix in cheddar, sour cream, egg, and pepper.
3. Fold drained squash into the cheese sauce. Transfer to a buttered 8-inch square (or 2-quart) baking dish.
4. Toss crushed crackers with melted butter. Scatter evenly over squash mixture. Bake at 350°F (175°C) until golden and bubbling, 30 to 35 minutes.
5. Let rest 10 minutes before serving.

Notes

The 30-minute salting time is hands-off and not included in the prep time above. Don’t skip it, it’s what keeps the casserole from turning watery.