Summer Vegetable Gratin

Summer Vegetable Gratin

The island fever has sunk in. I am in desperate need of a couple of days away from the island. Big time…

When I feel like this and express my need for a getaway to my husband, his go-to fix is that we go somewhere close by Virgin Gorda, typically within the Caribbean. However, while this is usually an acceptable option for me, this time I wanted to escape to a more city-like place. As I expected, his first suggestion was San Juan, Puerto Rico – the closest “city” to us by a mere 90 miles. But since we have already been there a couple of times recently, I let him know that I’d prefer we go to Miami instead. He agreed.

Summer Vegetable Gratin

I cannot tell you how much I am looking forward to this getaway. Restaurants, cafes, movie theaters, and shops… here I come!

Though I will say, island fever or not, I was pleasantly surprised at our not-so-supermarket on Virgin Gorda this week. On my typical Monday shopping trip, I spotted some fresh, good-looking zucchini and yellow squash. I grabbed a pound of each, not knowing what to make, but not willing to pass it up. After a little thought, I decided on a warm summer vegetable dish that I used to make all the time when I was living in Atlanta.

On Sundays, I used to go to the farmer’s market and buy whatever fresh summer vegetables I could get my hands on and make endless variations of this vegetable gratin. Though this time, I stuck with the original recipe which is made with zucchini, onions, yellow squash, and tomatoes.

Summer Vegetable Gratin

What I love about this recipe is how easy it is to throw together. I started by salting the vegetables, which helps draw out some of the juices, and ensures the gratin doesn’t turn out soggy. To do this, I placed them in a colander set over a bowl and lightly sprinkled them with roughly one teaspoon of salt.


While that was happening, I caramelized 2 thinly sliced onions. Next, I arranged the zucchini and squash slices evenly in a large pie pan. I spooned a quick dressing I made with olive oil, garlic, and thyme all over the vegetables.

I topped them off with the onions I had caramelized earlier. Prior to putting them in the oven, I decorated the top with sliced tomatoes. After 40 minutes in the oven, to give it a little bit of crunch, I sprinkled it with a breadcrumb and cheese mixture. After another 10 minutes in the oven, I ended up with a delicious summer vegetable gratin dish.

Summer Vegetable Gratin


A couple notes to mention here:

1. I’d recommend that you pick vegetables that are similar in size. It really helps with even cooking and results in a more visually appealing final product.

2. Dry vegetables with paper towels as much as you can.

3. If you want to switch things up a little, you can substitute one of the squash with an eggplant. If you can find them, I would recommend Asian eggplant. Once you slice them, allow them to sit in bowl of salty water for 30 minutes. Salty water helps with eliminating some of the bitter taste typical of eggplant.
4. If you are calorie conscious, you can eliminate the cheese and make a quick garlic yogurt sauce to top it off. To make it, I mix 3 tablespoons of fat-free plain yogurt, with 2 cloves of minced garlic, a teaspoon of lemon juice, and a pinch of salt.
A dollop of garlic yogurt on top gives this a very Mediterranean-like taste.


Summer Vegetable Gratin

1 Star2 Stars3 Stars4 Stars5 Stars (No Ratings Yet)


from reviews

  • Prep Time: 15 minutes
  • Cook Time: 50 minutes
  • Total Time: 1 hour 5 minutes
  • Yield: 4


  • 2 medium-sized zucchini, cut into 1/4 inch slices
  • 2 medium-sized yellow squash, cut into 1/4 inch slices
  • 2 large tomatoes, cut into 1/4 inch slices
  • 4 tablespoons olive oil – divided
  • 2 medium onions, sliced thinly
  • 3 cloves of garlic, minced
  • 1 tablespoon fresh thyme, chopped
  • 1 slice white sandwich bread
  • 1 cup Parmesan cheese, grated
  • 1 shallot, sliced thinly
  • 2-3 tablespoons fresh basil, chopped
  • Salt and black pepper


  1. Place zucchini and yellow squash slices in a colander set over a bowl. Toss it with 1 teaspoon table salt and let it sit on the kitchen counter for 30 minutes.
  2. Line a baking sheet with a couple of sheets of paper towel. Place the tomato slices on the baking sheet in one layer. Evenly sprinkle them with 1/2 teaspoon salt. Let it sit on the kitchen counter for 30 minutes.
  3. Pre-heat oven to 400 F degrees.
  4. Heat 1 tablespoon of olive oil in a large skillet (I used my cast iron skillet). When it is sizzling hot, place the onions. Sprinkle it with 1/2 teaspoon salt and 1/4 teaspoon black pepper. Cook them, stirring frequently, until they are caramelized, 20-25 minutes.
  5. Mix olive oil, garlic, and thyme in a small bowl.
  6. Drain the water from the zucchini and yellow squash slices. (I also used a paper towel to pat-dry them as much as I could.) Equally distribute half of the vegetables in a 10-inch pie plate. Spoon half of the olive oil mixture over. Continue with the rest.
  7. Place the caramelized onions in an even layer on top of the zucchini and yellow squash slices.
  8. Slightly overlap tomato slices in a single layer on top of the onions.
  9. Spoon the rest of the olive oil mixture evenly over tomatoes.
  10. Place it in the oven and bake for 40 minutes.
  11. Place the bread in a food processor and pulse until it turns into breadcrumbs, 6-8 pulses. Place it in a bowl. Mix in the Parmesan cheese and shallot slices.
  12. Remove baking dish from the oven. Increase the temperature to 450 F Degrees.
  13. Sprinkle the breadcrumb mixture evenly on top of tomatoes. Bake for another 10 minutes.
  14. Allow it to cool for 10 minutes. Sprinkle it with basil and serve.

This recipe is adapted (with minor changes) from America’s Test Kitchen.

Summer Vegetable Gratin

Add a comment...

Your email is never published or shared. Required fields are marked *

Hi There!

I am so glad you stopped by and I hope you are enjoying my adventures in cooking, photography, and life. 
I am Aysegul: the photographer, writer, designer, recipe creator, and dishwasher behind this blog. This website is a journal of my favorite seasonal and healthy recipes. Click around and let me know if I can help in any way. 
Meanwhile, if you make one of my recipes please use the hashtag #flprfeats so that I can see it. If you want to follow along with what I am up to on a daily basis you can follow me on Instagram and Facebook.