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The squash looks almost dry when you lift it from the pot, then a puddle gathers at the bottom of the casserole dish. That happened in my first batch of Southern yellow squash casserole, and it left the cracker topping soft underneath. Now I take an extra moment to drain the squash well before it goes anywhere near the creamy filling.

The balance here is what makes this casserole comforting without turning it heavy: tender squash and onion, a tangy sour cream mixture, sharp cheddar, and a buttery cracker top. I keep the squash slices even so they soften at the same pace, and I let them cool before stirring them into the eggs. The top bakes to a golden crunch while the middle stays soft and set, ready to scoop into generous portions.

Why This Squash Casserole Needs a Thorough Drain Before the Creamy Filling

Yellow squash carries plenty of moisture, and simmering it softens the flesh while drawing out even more. If that liquid follows the squash into the baking dish, it thins the sour cream and egg mixture. The casserole may still brown on top, but the center can turn loose and watery rather than holding a creamy scoop.

Drain the squash and onion in a colander, then press gently to help the excess liquid escape. Gentle matters: squash that’s mashed at this stage loses the tender pieces that give each serving its texture. You’re looking for slices that are soft enough to fold into the filling but still recognizable, with no pool of cooking liquid underneath them. That small bit of care lets the filling set around the squash instead of swimming around it.

What the Squash, Cheddar, and Cracker Topping Each Bring

• Yellow squash — Choose firm squash without soft spots, then trim and slice it evenly so the pieces cook at the same rate. Fresh squash holds its shape through the short simmer better than thawed squash, which tends to soften and release extra moisture.
• Yellow onion — Finely chopping the onion distributes its savory sweetness through the filling without leaving big, crunchy pieces. A yellow onion fits the mild squash without overpowering it.
• Sour cream and mayonnaise — Sour cream brings tang, while mayonnaise gives the filling a fuller, smoother texture. Full-fat versions make the richest filling; plain full-fat Greek yogurt can replace the sour cream in the same amount for a slightly tangier, less rich result.
• Eggs — The eggs help the creamy mixture hold together after baking, so use large eggs and whisk them thoroughly with the sour cream and mayonnaise before adding the squash.
• Sharp cheddar — Sharp cheddar brings enough savory flavor to stand up to the squash and creamy base. Cheese shredded from a block melts smoothly; pre-shredded cheddar is convenient and works, though it may not melt quite as evenly.
• Buttery round crackers and butter — The crackers give the top its crisp, salty contrast, and melted butter coats the crumbs so they brown in the oven. Crush them into small pieces rather than a fine powder for a topping with more texture.

From Tender Squash to a Golden, Set Casserole

Simmer the squash until just tender

Heat the oven to 350°F and coat a 9×13-inch baking dish with nonstick cooking spray. Put the sliced squash, finely chopped onion, water, kosher salt, and black pepper in a 5-quart pot. Bring the mixture to a boil, cover the pot, and simmer for 8–10 minutes, stirring once. The squash should be tender but still hold its shape; if the slices are falling apart, they’ve gone past the texture you want.

Drain well, then cool before mixing

Tip the squash mixture into a colander and let the liquid run off thoroughly. Press gently rather than crushing the slices, then leave the mixture to cool for 10 minutes. In a large bowl, whisk the eggs, sour cream, and mayonnaise until smooth. Stir in the cheddar and cooled squash mixture until the cheese and squash are spread throughout.

Coat the cracker crumbs in butter

Stir the crushed buttery round crackers with the melted unsalted butter until the crumbs are evenly coated. Look for crumbs that are moist and lightly clumped, not sitting in a pool of butter. This even coating helps the topping brown across the dish instead of leaving dry patches beside greasy ones.

Bake until the top is golden and the middle has set

Spread the squash mixture in the prepared dish and scatter the cracker topping evenly over it. Bake for 30–35 minutes, until the top is golden brown and the center reaches 160°F. If the surface colors before the middle is ready, loosely cover the dish with foil for the remaining bake time. Let the casserole rest for 10 minutes before serving so the filling has time to settle.

Two Easy Ways to Adapt the Cracker-Topped Casserole

Questions That Come Up When Making Squash Casserole

Southern Yellow Squash Casserole

Southern yellow squash casserole combines tender squash, sharp cheddar, and a creamy filling under a buttery cracker topping. Baked in a 9x13-inch dish, it has a golden top and a tender, savory center.

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Prep Time 20 minutes mins

Cook Time 42 minutes mins

resting 10 minutes mins

Total Time 1 hour hr 12 minutes mins

Servings: 8 servings

Course: Side Dish

Cuisine: Southern

Calories: 410

Ingredients Equipment Method Notes

Ingredients

  

For the squash filling

• 1 tsp nonstick cooking spray
• 2.5 lb yellow squash trimmed and sliced 1/4 inch thick
• 1 yellow onion medium, finely chopped
• 0.5 cup water
• 1 tsp kosher salt
• 0.25 tsp black pepper
• 2 eggs large
• 1 cup sour cream
• 0.5 cup mayonnaise
• 1.5 cup sharp cheddar cheese shredded

For the cracker topping

• 1 sleeve (about 32) buttery round crackers crushed
• 4 tbsp unsalted butter melted

Equipment

• 1 9x13-inch baking dish

Method

 

Cook and mix the filling

1. Heat the oven to 350°F.
2. Coat a 9x13-inch baking dish with the nonstick cooking spray.
3. Put the squash, onion, water, salt, and pepper in a 5-quart pot.
4. Bring the mixture to a boil.
5. Cover and simmer for 8–10 minutes, stirring once, until the squash is tender.
6. Drain the squash mixture thoroughly in a colander, pressing gently to remove excess liquid.
7. Let the squash mixture cool for 10 minutes.
8. In a large bowl, whisk the eggs, sour cream, and mayonnaise until smooth.
9. Stir in the cheddar and drained squash mixture.

Make the topping

1. Stir the crushed crackers and melted butter together until evenly coated.

Assemble and bake

1. Spread the squash mixture in the prepared baking dish.
2. Scatter the cracker topping evenly over it.
3. Bake for 30–35 minutes, until the topping is golden brown and the center reaches 160°F.
4. Let the casserole rest for 10 minutes before serving.

Notes

Press the drained squash gently but thoroughly to keep excess liquid from making the casserole watery. Refrigerate leftovers for 3–4 days; freezing is not recommended because the creamy filling can change texture. For a lighter option, plain Greek yogurt can replace the sour cream.