Cheesy Squash Casserole.

This is not a casserole blog. I’m not a casserole person. But I love this squash casserole. So it’s not exactly representative of what I typically cook, but after toying with the idea of having a food blog for…years…for some reason, this was the day. Because, you know, nothing screams “take on a new project!” like having a 10-week-old baby.

It didn’t seem like the worst time to jump into blogging, since the casserole was for a church event and I wasn’t actually making “dinner” with a hungry family waiting to eat it. So I started taking pictures. Please don’t mind the fact that I hadn’t cleared any of the junk highly necessary items off of the counters.


Jay’s parents had a super successful garden this summer. Like…I couldn’t figure out why they kept bringing us bagsuponbagsuponbags of vegetables, until one week they were out of town and Jay, our older daughter, and my extremely pregnant self took care of harvesting. And I gained a whole new appreciation for farmers and pioneers and anyone who has ever picked a zillion green beans at 3 pm in 90 degree heat while great with child. So…we ate a lot of vegetables this summer. And we froze a lot of vegetables. I have lots…LOTS…of bags just like this in our freezer. The moral of this story, however, is that I have no idea how much squash this is. This is a bunch of sliced, parboiled squash, and that is all I have to say about that.

I had made this casserole (Ina Garten’s Zucchini Gratin) once before, and followed the recipe exactly, so I can tell you it works perfectly as she wrote it (which should surprise no one – she’s the best). I can also tell you it works perfectly if you measure almost nothing and make roughly 1-1/2 times the amount and bake it right in the cast iron skillet with shameful amounts of crunchy, cheesy topping.

My older daughter LOVES to help in the kitchen. She found two big onions for me in the pantry. She’s wearing pjs…because pjs > clothes, obviously.

I sliced them into thin half-moons and then cut those in half.
Ina’s recipe called for 6 tablespoons of butter, which seemed excessive to me, so I used 4 tablespoons in this big batch. I felt confident about cutting it down since all summer my go-to squash “recipe” was to throw 2 tablespoons of butter, one sliced onion, and 4-ish squash (squashes?)…more or less depending on their size…in a skillet for around 30 minutes, with plenty of salt and pepper, letting it barely caramelize at the end. So simple and good. This casserole just takes things a few delicious steps farther.
Because my squash was already partly cooked, and because Ina said to, I cooked my onions alone for a while in the butter. In this skillet and on my stove, medium was a good temperature to get them softened but not brown. And really, if they start to brown, no harm done!
Then I added my thawed squash and generously seasoned with kosher salt and pepper. Yellow squash doesn’t have a ton of flavor on its own, so don’t be shy, and taste as you go!

I did measure the nutmeg since since I didn’t want it to be overpowering, and stuck with Ina’s 1/4 teaspoon even though I was increasing the other ingredients.

Once the onions and squash had cooked down and most of the liquid that had been cooking out had evaporated, I sprinkled on the flour (about 3 tablespoons) and stirred that around for a minute, then added 1-1/3 cups of warm milk and let it thicken on low heat for a couple of minutes.

 While the squash was cooking, I discovered that I had no bread, no dry breadcrumbs, no panko, no nothing. I had a freezer bag with less than half a cup of whole wheat bread crumbs left from something sometime, and then I dug up a few pieces of baguette in the freezer. I lightly toasted them and put it all in the food processor.

Ina uses gruyere cheese, but I was going with what I had on hand, so I used half a block of cheddar (Cabot Extra Sharp – it’s my favorite, favorite, favorite) and a chunk of asiago, for about 1-1/2 cups total. I doubled the topping ingredients, since I had a lot of surface area in the cast iron skillet. Plus it’s arguably the best part.

I combined the cheese and bread crumbs and sprinkled it right over the squash and onions. I drizzled a little olive oil over the top and stuck the whole thing in the oven. You could definitely transfer to a casserole dish, and I think this large version still would have fit in a 9×13 pan. But I loved the look in the cast iron skillet, and not having to wash an extra dish!


I baked the casserole for 20 minutes at 400 until it was bubbly and brown. At this point, my older daughter was making sad, grumpy noises which is when I realized I hadn’t given one.single.thought to what I was going to feed her for dinner. Whoopsies. Fortunately, since she was all hopped up on a-babysitter-is-coming adrenaline, she thought scrambled eggs sounded good. With a side of leftover brown rice. With a side of grapes. With a side of carrots, with a side of peanut butter. Also known as a big plate of things that shouldn’t be on the same plate.

Then I almost failed at my first bloggable recipe when I forgot to take a picture of the final product until it was riding in the passenger seat!

This Thanksgiving-esque spread was in celebration of the five year anniversary of our church’s first worship service. It was a serious feast, and so sweet to eat together and rejoice in God’s work over the last five years.

squash casserole for thanksgiving

And the casserole was delicious! Make it for Thanksgiving or a potluck or dinner…or weekly, because we haven’t even dented the Squash Stash.

Cheesy Squash Casserole.

Yield: 8 servings

Cheesy Squash Casserole.


  • 4 tablespoons butter
  • 2 large onions, sliced
  • 6 medium yellow squash, sliced (or zucchini, or a combination - frozen is fine!)
  • kosher salt and pepper
  • 1/4 teaspoon nutmeg
  • 3 tablespoons all-purpose flour
  • 1-1/3 cups milk, warmed (I used 1%, but use whatever you have on hand)
  • 1-1/2 cups fresh breadcrumbs (or about half that amount of regular dry breadcrumbs or panko)
  • 1-1/2 cups freshly grated cheese (cheddar, Gruyere, asiago - use your favorite or a combination!)
  • a drizzle of olive oil (or more butter)


Preheat the oven to 400. Melt the butter in a 12-inch cast iron skillet (or other large ovenproof skillet, if you plan on baking in the pan) and sauté the onions for 5-10 minutes on medium-low to medium heat to soften. Add the sliced squash and season with salt, pepper, and nutmeg. Cook for 15-20 minutes (if using frozen, partially cooked squash, this may take less time), until cooked down (the liquid they release will have mostly evaporated). Sprinkle with flour and stir to cook for 1 minute. Add milk and stir, letting the mixture thicken over low heat for 2-3 minutes. To cook in the skillet, sprinkle with combined breadcrumbs and cheese, or transfer to a large baking dish (9x13 or bigger) before topping. Drizzle with oil or dot with bits of butter, and bake for 20 minutes until the topping is brown and crispy and beautiful!


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  1. Barb (Bet's Mom)

    Having eaten large helpings of this deliciousness, I can vouch for how tasty it is! (Even if you don’t have the bonus of help from my adorable pj-clad granddaughter.)

  2. Mmmm, I would be happy to participate in a Cheesy Squash Casserole Taste Test, should the opportunity arrive.

  3. Made this tonight for the first time! I halved it and baked it in an 8×8 dish, and used cheddar. I must confess to not knowing what Gruyere cheese tastes like, but I want to make this again and try it out. :o)

    1. You’ll feel so fancy! If a casserole can ever be fancy… 😉

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