This easy squash casserole combines tender yellow squash in a super creamy, cheesy sauce, all topped off with a buttery cracker topping for a crowd-pleasing summer side dish for potlucks, picnics, holidays, and cookouts!

A Southern squash casserole is a crowd-pleasing, comforting family-friendly classic – and with good reason. Not only is it a great way to use up a bounty of squash (or zucchini), but the combination of squash, a super creamy, cheesy sauce, and crunchy butter cracker topping is a cozy, satisfying must-have at ANY gathering. It’s ready to serve with roast chicken, baked salmon, brisket, pork chops, ribs, etc.

It’s also really simple to prepare. Just par-cook the squash (to remove excess liquid for a foolproof summer squash casserole that’s NEVER mushy or soggy). Then prepare the remaining layers, assemble, and bake. It’s even make-ahead and freezer-friendly, which is great as it’s sure to be highly requested by friends/family.

Looking for more ways to enjoy yellow squash/zucchini? Why not try fried yellow squash, sautéed zucchini, or Air Fryer zucchini fries?

Squash Casserole Ingredients

This squash casserole recipe needs fewer than a dozen simple, easy-to-find kitchen and pantry ingredients.

• Summer squash: It’s best to use yellow squash that is more on the smaller to medium side, as they often have fewer seeds and a sweeter, better taste. However, I had larger squash this time. Zucchini will work just as well in the recipe.
• Onion: I used a yellow onion, though sweet onion will work amazingly, too.
• Oil: Use neutral-flavored cooking oil, like olive oil or avocado oil.
• Eggs: Eggs work as a binder within the casserole while providing protein and extra creaminess in the sauce.
• Thyme: Just a little fresh thyme is all you need to complement the delicate squash.
• Dairy: To give the casserole its signature creamy texture, you’ll need:
  • Sour cream (OR Greek yogurt),
  • Soft cream cheese (plain),
  • Cheddar cheese (and/or Swiss cheese/gruyere + optionally parmesan).
• Salt & black pepper: To season the yellow squash.
• The topping: Create a perfectly buttery, crunchy casserole topping with Ritz crackers and butter (unsalted works best). Italian breadcrumbs would also pair well.

How to Make the Best Squash Casserole

First, rinse and slice the squash into 1/3-14-inch rounds. Then, preheat the oven to 350°F/175ºC and grease a 9.5×6.5 inch casserole/baking dish.

Pre-cook the Squash

Heat the oil in a large skillet over medium-high heat until the oil shimmers. Then add the onion and sauté for two minutes.

Add the summer squash pieces and cook, loosely covered, for 10 minutes, until the center of the squash becomes tender.

If you don’t have a skillet large enough, you may have to do this in two batches or two separate pans.

Add the thyme, salt, and pepper, stir, and cook for 2-3 minutes uncovered for some of the liquid to evaporate.

If there’s still a LOT of liquid in the pan and you prefer a drier casserole, drain the mixture through a colander for 5 minutes.

Prepare the Cream Sauce

Meanwhile, in a large bowl, combine the eggs, cream cheese, sour cream, and between ½-⅔ of the shredded cheese and whisk/mix until thoroughly combined.

Make the Cracker Crumb Topping

Melt the butter on the stovetop or in the microwave (for 20-30 seconds).

Then crush the crackers into a crumb consistency by placing them in a Ziplock and bashing them with a rolling pin or the bottom of a heavy pan. Add the melted butter to the crushed cracker crumbs in a small bowl and mix thoroughly.

Assemble the Squash Casserole

Spread the par-cooked squash mixture into the prepared baking/casserole dish, then pour over the cream sauce and mix well.

Sprinkle over the remaining shredded cheese and cracker mixture, spreading it evenly over the top. Then transfer the dish to the oven to bake.

How Long to Cook Squash Casserole?

Bake the casserole until it’s golden brown on top with a bubbly filling – this should take about 20 minutes.

Optionally broil it for a minute or two at the end if it hasn’t browned enough.

Leave it to sit for just a few minutes (3-5) before serving to allow it to thicken up slightly.

Top Tips for Texture and Flavor in Squash Casserole

• Slice the squash evenly: Use a mandoline for perfectly even pieces that cook evenly.
• Par-cook the squash (about half cooked): This step is important to achieve the best tender texture once baked and remove excess liquid from the squash to avoid a watery casserole.
• Don’t overcrowd the squash: For the best consistency, par-cook it in batches or separate skillets so they are more evenly cooked.
• Customize the moisture levels: Draining the squash thoroughly after par-cooking will create the driest, richest casserole. Keep some or all of the liquid for a slightly wetter casserole with enhanced flavor (as the liquid contains flavor, too). It’s up to you.
• Be careful not to overbake it: As this could lead to a mushy casserole.

Can You Make Squash Casserole Ahead of Time?

There are three ways to prep this yellow squash casserole in advance.

1. Firstly, you could par-cook the squash several days in advance and store it in an airtight container in the refrigerator, ready to complete the recipe.
2. Assemble the casserole in the baking dish (minus the buttery cracker toppings) and refrigerate it wrapped tightly in plastic wrap in the fridge for up to 2 days in advance. When you’re ready to bake, let it sit at room temperature for 30 minutes, add the cracker topping, then bake following the recipe instructions.
3. Assemble the casserole (minus the topping) in a double foil-lined baking tray, leaving a foil overhang to fold over the top of the casserole. Freeze until solid, then wrap in more aluminum foil/plastic wrap and freeze for up to 3 months. To bake, leave it to thaw overnight in the fridge, bring to room temp, add the buttery cracker crust, and bake.

How to Store Squash Casserole

In the Fridge: Allow the yellow squash casserole to cool, then store leftovers either wrapped with plastic wrap or in separate airtight containers for 3-4 days.

In the Freezer: I prefer freezing it unbaked, minus the topping. However, you can freeze leftovers by waiting for them to cool, then tightly wrapping them in foil/plastic wrap to store for 3 months. Allow them to thaw in the fridge overnight before reheating.

To reheat: It’s best to reheat the leftovers in the oven at 350ºF/175ºC until piping hot and slightly crisp on top once more (20-30 minutes, based on how much there is).

More Easy Casserole Recipes

• Tuna Casserole (With Noodles)
• Easiest Corn Casserole
• Fabulous Cheesy Potatoes
• cabbage casserole

If you try this easy summer squash casserole recipe, I’d love to hear your thoughts/questions below. Also, I’d appreciate a recipe card rating below, and tag me in your recipe recreations on Instagram @Alphafoodie!