Summer Vegetable Gratin

July 22, 2009 · 26 comments · Print This Post

in Dinner, Vegetarian

Summer Vegetable Gratin

In the summer time my mind doesn’t normally think, “Eureka! Let’s make a casserole.” But perhaps it should? The rainbow of produce I picked up at the Copley Square Farmers Market seemed destined for greatness so when I stumbled upon this light and eye appealing recipe I knew I had found a match made in heaven.

My memories of casseroles as a child included the affectionately named “Tuna Pea Wiggle.” This was actually a traditional tuna casserole made with canned tuna, peas, egg noodles, and cream of mushroom soup. All ingredients, that notoriously picky as I was as a kid, should have brought me to an ear shattering meal time tantrum. But there was something about those bright green peas and the laughable recipe title that made it a top choice in my book.

One of my favorite dinnertime dishes growing up that actually held over to my adulthood is a comforting concoction of ground beef, Campbell’s Tomato Soup, green beans, and mashed potatoes. This hearty one pan supper was known as “Green Bean Casserole” not to be confused of course with the funky French Onion topped mess that always seems to find its way onto every table at Thanksgiving. I’ve tried to help this childhood favorite out a bit in recent years adding garlic and sautéed onion to the ground beef, using freshly steamed green beans, and topping it all with garlic-parmesan mashed potatoes. Interestingly enough when I tried to substitute Amy’s Tomato Soup for the Campbells I found that I just didn’t like the taste. This absolutely shocked me since I normally shout the glory of this particular Amy’s soup at the top of my lungs. It just goes to show that some things simply shouldn’t be meddled with.

In the end the Summer Vegetable Gratin recipe came out beautifully. It’s a bit time consuming, what with all of the salting and draining and paper towel patting of the vegetables, but the result is a dreamy dish of flavorful zucchini, summer squash, tomatoes, and onions that’s simply addictive. The first evening we ate the dish as our entree and the next day I cooked some nutty brown rice and served the leftovers over the top. Every last bite of this technicolor casserole was happily consumed and I’m thoroughly looking forward to my next Farmers Market trip so I can make it again.

Summer Vegetable Gratin

Summer Vegetable Gratin
Originally published in the July 2008 edition of Cook’s Illustrated
Serves 6-8 as a side or 4 as a light main dish

6 tablespoons extra-virgin olive oil
1 pound zucchini, ends trimmed and sliced crosswise into 1/4-inch-thick slices
1 pound summer squash (yellow), ends trimmed and sliced crosswise into 1/4-inch-thick slices
2 teaspoons table salt
1 1/2 pounds ripe tomatoes (3 to 4 large), sliced 1/4 inch thick
2 medium onions, halved lengthwise and sliced thin pole to pole (about 3 cups)
3/4 teaspoon ground black pepper
2 medium garlic cloves, minced or pressed through garlic press (about 2 teaspoons)
1 tablespoon minced fresh thyme leaves
1 large slice white sandwich bread, torn into quarters (Erin’s Note: I used 1 cup of Panko Bread Crumbs)
2 ounces Parmesan cheese, grated (about 1 cup)
2 medium shallots, minced (about 1/4 cup)
1/4 cup chopped fresh basil leaves

Adjust oven rack to upper-middle position and heat oven to 400 degrees. Brush 13- by 9-inch baking dish with 1 tablespoon oil; set aside.

Toss zucchini and summer squash slices with 1 teaspoon salt in large bowl; transfer to colander set over bowl. Let stand until zucchini and squash release at least 3 tablespoons of liquid, about 45 minutes. Arrange slices on triple layer paper towels; cover with another triple layer paper towels. Firmly press each slice to remove as much liquid as possible.

Place tomato slices in single layer on double layer paper towels and sprinkle evenly with 1/2 teaspoon salt; let stand 30 minutes. Place second double layer paper towels on top of tomatoes and press firmly to dry tomatoes.

Meanwhile, heat 1 tablespoon oil in 12-inch nonstick skillet over medium heat until shimmering. Add onions, remaining 1/2 teaspoon salt, and 1/4 teaspoon pepper; cook, stirring occasionally, until onions are softened and dark golden brown, 20 to 25 minutes. Set onions aside.

Combine garlic, 3 tablespoons oil, remaining 1/2 teaspoon pepper, and thyme in small bowl. In large bowl, toss zucchini and summer squash in half of oil mixture, then arrange in greased baking dish. Arrange caramelized onions in even layer over squash. Slightly overlap tomato slices in single layer on top of onions. Spoon remaining garlic-oil mixture evenly over tomatoes. Bake until vegetables are tender and tomatoes are starting to brown on edges, 40 to 45 minutes.

Meanwhile, process bread in food processor until finely ground, about 10 seconds. (You should have about 1 cup crumbs). Combine bread crumbs, remaining tablespoon oil, Parmesan, and shallots in medium bowl. Remove baking dish from oven and increase heat to 450 degrees. Sprinkle bread-crumb mixture evenly on top of tomatoes. Bake gratin until bubbling and cheese is lightly browned, 5 to 10 minutes. Sprinkle with basil and let sit at room temperature 10 minutes before serving.

Summer Vegetable Gratin

{ 24 comments… read them below or add one }

1 ttfn300 July 22, 2009 at 8:03 pm

hehe, tuna pea wiggle 🙂 this looks like a great way to showcase summer veggies!


2 Monica H July 22, 2009 at 11:01 pm

Pretty casserole! I don’t think I’ve ever said that before.


3 Elina July 23, 2009 at 9:12 am

Erin, this looks incredible! I love trying to use up farmers market produce in interesting ways – this looks like the perfect way to do it! 🙂


4 Tabby Kelliher July 23, 2009 at 10:39 am

Hi Erin,

Now this I can cook and will! All my favorite veggies in one place….mmm! Yours came out so beautiful. Thanks for another great recipe.


5 Kerstin July 23, 2009 at 11:26 am

This looks like the perfect summer dish and I love the panko on top!


6 Marilyn July 23, 2009 at 12:36 pm

Erin, this looks terrific – making a baked dish look, well, “fresh” in summer really take some doing. Delicious job!


7 Sues July 23, 2009 at 1:13 pm

This is pretty much my dream come true!! And it’s so pretty too 🙂 Definitely not your grandma’s casserole!


8 Bob July 23, 2009 at 2:23 pm

That looks fantastic, I love casseroles. Next time I manage to hit the farmers market I’m trying this out!


9 The Gypsy Chef July 23, 2009 at 8:23 pm

This looks delicious. I’ve been looking for a vegetable recipe for this Saturday, this one fits the bill!
Nice photographs!


10 Hillary July 24, 2009 at 11:06 am

Beautiful summer side dish! You should submit this recipe to!


11 EMC July 24, 2009 at 1:30 pm

I too grew up with casseroles that included potato chip crusts and cream of mushroom soup. Even though this is a gratin, you should proudly proclaim to all that it is in fact a casserole! I love summer produce, and this looks like the perfect side dish to wipe away all those bad memories.


12 Kelly July 24, 2009 at 10:09 pm

Great post. I think you’re a lot more logical than I am. For some reason I often think about soups and casseroles and other weather inappropriate things in the summer. I also loved the bit of nostalgia. I pretty much grew up on casseroles as a kid so I can relate to that part of the post a lot. 🙂 I especially love looking at old church cookbooks to look for the particularly horrific ones.


13 Jess July 25, 2009 at 11:58 pm

You’re right – I don’t usually associate gratin with summer. But this looks just perfect for a summer night. I’ve printed out the recipe and plan on making it next month. Thanks!


14 nithya at hungrydesi July 26, 2009 at 11:58 am

Looks fresh and delicious!


15 Bren July 27, 2009 at 10:33 am

i hear you on all that patting and drying. as much as i hate to admit, those are the types of details that keep me using my pressure cooker! i love this dish, though! it’s the epitome of a summer offering.


16 saramariesue July 28, 2009 at 10:22 am

I made this last night after you posted it. It tastes as good as the pictures look. So yummy – I’ll definitely fix this up again. Thanks for sharing!


17 cassie August 5, 2009 at 10:47 pm

this looks absolutely yummy!! i must try!


18 Natalie August 6, 2009 at 12:51 pm

Thank you for sharing this. I’m making it tonight with some modifications due to not having yellow squash! Using some sweet japanese eggplants from my parents’ garden instead (still using the zucchini, tomatoes and onions)


19 Karly August 27, 2009 at 7:20 pm

Oh my word, this looks delicious!


20 Jane July 10, 2010 at 10:00 pm

Best zucchini recipe EVER!! I made it tonight and could have eaten the whole pan myself – and I don’t like zucchini. My csa delivered one this week and I’m so glad I found your blog. Thank you!


21 Nancy July 16, 2010 at 12:16 pm

came across this exact recipe on Americas Test Kitchen. Yum


22 Kim June 23, 2019 at 5:28 pm

This recipe came in my email the other day from Cook’s Illustrated. It sounded so good that I knew I had to try it. After reading it, I bookmarked it and opened again to check the ingredients and then again while shopping. When I got home to actually make it and opened it for the forth time, I hit a paywall! So I was very, very glad to find this recipe on your blog. It is superb though a little bit of a pain in a small kitchen with limited counter space. Picture tomatoes on the washing machine, zucchini on the dining room table, and so forth! I used all fresh herbs from my garden and really good Parmesan Reggiano. 2 ounces of parm yielded way more than a cup with my microplane and one shallot yielded 1/4 cup easily. I added fresh chopped Italian parsley to the breadcrumbs (which I had in freezer from leftover homemade baguettes). In spite of the time and trouble, I WILL make this again!


23 Alison July 12, 2019 at 5:34 pm

Can this dish be made ahead, or partially made ahead?


24 April 24, 2021 at 12:54 pm

Excellent site. Lots of useful info here. I’m sending it to a few buddies ans also sharing
in delicious. And certainly, thank you in your sweat!


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