By Julia Moskin
Updated Oct. 16, 2023
- Total Time
- 1½ hours
- Rating
- 4(248)
- Notes
- Read community notes
Cooking some of the ingredients beforehand is the key to a rich-tasting, nonsoggy gratin of summer vegetables: It pulls out water and concentrates flavors. The recipe has three layers — aromatics, vegetables and topping — but you can omit the topping to make it just two. Be sure to use fresh bread, nothing hard and stale, in that topping. Fluffy bits, not sandy shards, make the best crust.
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Ingredients
Yield:8 to 12 servings
- 2medium onions, thinly sliced
- ¼cup olive oil
- 2red bell peppers, thinly sliced, or 2 additional onions
- ½teaspoon red pepper flakes
- 4cloves garlic, smashed
- 1½pounds plum or other ripe tomatoes
- ¼cup olive oil
- 1baguette
- 1cup shredded Parmesan or Gruyère cheese
- ¼cup olive oil, more for baking
- 1½pounds zucchini, sliced ¼-inch thick
- 1½pounds yellow squash, sliced ¼-inch thick
- ¼cup freshly chopped basil or parsley, more for garnish
- Salt and black pepper
For the Base Layer
For the Optional Tomato-bread Crumb Topping
For the Gratin
Ingredient Substitution Guide
Nutritional analysis per serving (10 servings)
369 calories; 22 grams fat; 5 grams saturated fat; 0 grams trans fat; 13 grams monounsaturated fat; 2 grams polyunsaturated fat; 37 grams carbohydrates; 4 grams dietary fiber; 12 grams sugars; 10 grams protein; 726 milligrams sodium
Note: The information shown is Edamam’s estimate based on available ingredients and preparation. It should not be considered a substitute for a professional nutritionist’s advice.
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Preparation
Step
1
Make the base layer: In a large, heavy ovenproof skillet or enameled cast-iron pan (10 to 12 inches across), combine onions and olive oil and heat to a sizzle, stirring to separate. Add bell peppers, red pepper flakes and garlic. Cook, stirring, over low heat until peppers are very soft and onions are browned, about 20 minutes. Remove from heat and remove garlic, leaving remaining mixture in the pan.
Step
2
Meanwhile, make the topping (if using): Core tomatoes and slice them ¼ inch thick. Lay on paper towels to drain for 10 minutes. Heat 2 tablespoons oil in a large skillet over low heat. Add tomatoes and cook very slowly, turning once or twice, until liquid has bubbled away and flesh is cooked through, about 8 minutes. (Do not overcook, or tomatoes will fall apart.) Turn off heat and let slices cool in skillet; they will continue to dry out. Tear baguette into pieces and pulse in a food processor to make coarse, fluffy, pea-size crumbs. Add remaining 2 tablespoons oil and the cheese and pulse to combine.
Step
3
Assemble the gratin: Heat oven to 425 degrees. (If your oven has a convection feature, use it, reducing baking temperature to 400 degrees.) In a large bowl, combine oil, zucchini and squash, and toss well until lightly and evenly coated. Add basil, sprinkle generously with salt and pepper, and toss again.
Step
4
On top of the base layer in pan, arrange squash and zucchini slices around the inner rim of the pan, standing on their edges in roughly alternating colors. Pat down into the pan so slices overlap and lie down, like shingles or fallen dominoes. Repeat to make another circle inside the first, and again if necessary, until pan is filled. Sprinkle with salt and pepper.
Step
5
Brush oil over the top of the gratin and transfer to oven. Bake 30 minutes. Raise oven temperature to 450 degrees (425 degrees for convection), or heat the broiler.
Step
6
If not using topping, brush surface again with oil. If using topping, arrange tomato slices in one layer on top of the par-baked gratin. Spread bread-cheese mixture over tomatoes and press down gently.
Step
7
Bake or broil until vegetables are browned around the edges or crust is crisp and golden. Let cool slightly and serve hot or at warm room temperature. Garnish each serving with herbs.
Ratings
4
out of 5
248
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Cooking Notes
Nancy P
I make a similar gratin without the bread topping, with the difference that it is baked at 400 degrees for 70 minutes followed by a resting period of 10 min out of the oven (eliminating the pre-cooking phase). The topping I use is chopped herbs and grated parmesan cheese. The recipe comes from Fine Cooking a few years ago and has never failed.
PollyW
Could this be made ahead and reheated just before serving?
annah
This is a terrific recipe, really robust flavor and the crust was revelatory (I usually use panko, often with oil in it). I made it using a 10" wide LeCreuset casserole and had far more zucchini slices than I could fit in the pan. I was skeptical that the zucchini would cook in 30 minutes, but it did. I used a mix of romas and slicing tomatoes and the latter did fall apart. I used all onions in the bottom layer as I thought the pepper might be a distraction. Great recipe/method/video.
Kim F
We made this with veggies from the garden - and it was perfect. Finally, a vegetable casserole without all that water. Silky, flavorful, and a great main entree for a summer night. The video made the assembly very easy to follow. Well done Ms Moskin!
John
We thoroughly enjoyed this. I used a red and a green bell pepper, and I also added a hatch pepper. It was even better the next morning, warmed, with a fried egg over each serving.
Kirsten
I followed the recipe to the letter, and it burned while baking in a 425 oven after sauteeing the aromatics for 20 minutes until the onions were brown. The topping was so excessive--the quantity of bread overwhelmed. And who has a skilled that fits 1.5 lbs of tomatoes sliced to 1/4 inch? Was this recipe tested?
mjan
The tomatoes can be left out. My daughter despises them, but loves zucchini. When I make this, I add eggplant slices trimmed into wedges to about the same size as the zucchini and squash. The topping without the tomatoes is still a nice touch.
Andrea
The vegetable preparation, while more involved than in other gratin recipes, makes for a delicious dish. The crust, however, is a bit problematic. Fresh bread crumbs were a revelation - but an entire baguette is way too much. Mine, from Whole Foods, yielded an enormous quantity of crumbs. About twice as much as there seemed to be in the video. I used half. Even so, this was far too much and overwhelmed even a very well-packed cup of Parmesan.
Fxl Shultz
I have made this over and over—it’s a hit every time. My preferred ingredients include zucchini, sliced Japanese eggplant, and a handful of fennel slivers over the slices and under the tomatoes. I usually forget to buy the yellow squash, but if I remember, in it goes. I always use Panko instead of fresh bread crumbs. This dish really tastes of summer!
Fxl Shultz
And I mince the garlic and leave it in.
PD Molander
This was delicious and not at all soupy, like many gratins.
Samara
It's a lot of chopping, but I proclaim it Worth It! I did substitute a cup of panko breadcrumbs instead of fresh from a baguette and it was still delicious. A great way to use up all of that summer squash and zucchini.
igloopants
This is a favorite I look forward to making this every late summer, when my garden finally has zucchini, tomatoes and basil. I skip the red pepper and do the more onion option. And I always make the topping, using slicer tomatoes vs romas. Like others, I use panko for the breadcrumbs. I find the initial/no-topping baking phase takes longer than the 30 minutes stated, more like 40-45, followed by about 8 minutes for the topping. Pperhaps my zuke slices are stacked more upright than Julia's.
B Everett!!
this made Mark’s blood sugar go sky high. Maybe the bread crumbs or the cheese or both.
Fxl Shultz
I chop the garlic and leave it in, and I also add sliced Chinese eggplant. We love this and I have made it for several large parties it always receives rave reviews.
wendiem
This is really good!! I seasoned each step with thyme and a touch of herbs de provence, which added a little je ne sais quois.Can't go wrong with gruyere. A terrific way to use the bounty of our garden.
Eileen
This is wonderful. Big hit. Perfect for summer produce. I've halved it & reheated in the oven.
Ellen
I might keep elements of this but won't do the recipe again. My big fear came true, which was that it would be a soggy mess with all that zucchini -- just a ton of liquid at the bottom. Don't use a whole baguette for the topping, that would be insane...I used about a third of one and it was still more than I could use. Doesn't taste bad, though, so not a total miss!
Francesca
I love this recipe--and have made it so often that I'm comfortable making a few alterations. I now add thinly sliced Japanese eggplant and use a different fresh bread for the topping, which I drizzle with the leftover tomato oil. Adds just a hint of flavor. I use more garlic, as well, which I chop and leave in, and I add more onion. Extra herbs are also good.
michelem
We make all year round now and my family loves it! I don't bother with the tomatoes and bell peppers and just focus on the good spicy onion base along with the zucchini & squash center and fabulous gratin topping. It's beautiful to serve as well as yummy to eat.
MCG
I love this recipe! I roast the onions and garlic in the same pan in the oven, stirring occasionally, then added the pepper, cook. Then I layered the zucchini with spices, parmesan cheese in batches. No need to be "color coordinated," the final product does not reveal the colors. (learned this the first time I made this :) Added the bread/cheese topping sans tomatoes. I have roasted the onions/peppers a day ahead, then brought to room temp and layered accordingly. Saved a lot of time!
Janet
With the topping, this is a substantial vegetarian main. However, would not need that time-consuming Step 4, domino-arrangement of alternating vegetable slices, as it all gets covered over!
Linda
Delicious! This recipe gets my 'best summer recipe' vote. Thank you Julia.
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