Zucchini, Eggplant, Tomato Gratin

Try this French tian when you need a colorful vegetarian dish. Summer zucchini, eggplant, and tomatoes are all beautifully presented in a baked casserole gratin.

Zucchini Eggplant Tomato Gratin
Elise Bauer

Oh my. Look who's getting all fancy with the vegetables!

It's as if my garden decided to throw a prom, and the eggplants, zucchini, and tomatoes banded together to show everyone else up. (Clearly, they deserve best prize for something, don't you think?)

Normally I would look at something like this and think it's waaaay too complicated. But this summer vegetable gratin is actually quite straightforward.

To prepare these vegetables, you have to cut them anyway, so why not cut them in rounds and arrange them in a pretty pattern?

Zucchini Eggplant Tomato Gratin
Elise Bauer

Ratatouille or Tian Recipe?

If you recall, Remy, the "little chef" in Pixar's Ratatouille, prepared something similar for Anton Ego, the food critic. This isn't that dish, but something much easier.

You just sauté onions and bell peppers, layer them at the bottom of a casserole dish, top with rounds of eggplant, zucchini, and tomato. Top that with cheese and bake!

It's a lovely, easy, colorful presentation for our favorite summer vegetables. A perfect side to take to a party.

Slicing Vegetables for This Gratin

The zucchini, eggplant, and tomato in this recipe need to be sliced into 1/4-inch rounds. A mandolin will make short work of slicing the eggplant and tomato evenly and quickly. You can also use a food processor with a slicing disc. Slicing the vegetables evenly is a big part of this gratin's visual appeal, and ensures the veggies all cook at the same rate.

Very large tomatoes may need to be cut in half or into quarters so their diameter is close to that of the zucchini and eggplant.

Storing Leftover Gratin

Cover the dish and refrigerate 3 to 5 days. Reheat individual portions in the microwave or the entire dish in the oven at 350°F until just warmed through.

We don't recommend freezing this dish. The texture of the vegetables won't hold up once defrosted.

5 More Vegetable Side Dishes You'll Love

From the Editors Of Simply Recipes

Zucchini, Eggplant, Tomato Gratin

Prep Time 30 mins
Cook Time 70 mins
Total Time 100 mins
Servings 6 to 8 servings

We're topping this gratin with provolone and Parmesan cheeses. You could easily top it with gruyere instead. For a more Provençal approach, skip the cheese altogether and top with bread crumbs, minced garlic, parsley, and olive oil.


  • 3 tablespoons extra virgin olive oil, divided

  • 2 cups sliced yellow onion (about 1 large onion)

  • 1 cup sliced red, orange, or yellow bell peppers

  • 1 eggplant, about 1/2 pound (a slender eggplant like a Japanese eggplant, not a large globe)

  • 1 large zucchini or other summer squash, about 1/2 pound

  • 2 medium tomatoes

  • 3 cloves garlic, peeled and smashed

  • 1 1/2 teaspoons salt

  • 2 tablespoons chopped fresh parsley

  • 2 ounces provolone cheese, sliced or grated

  • 3 tablespoons grated Parmesan cheese


  1. Preheat the oven:

    Preheat the oven to 350°F. Place the oven rack in the center position.

  2. Sauté the onions and peppers:

    In a large sauté pan heat 2 tablespoons of the olive oil on medium high heat. Add the sliced onions and cook until lightly browned, stirring frequently, about 10 minutes.

    Add the sliced bell peppers and continue to cook with the onions until the bell peppers are softened and the onions are well browned, about 5 to 6 minutes more.

    Elise Bauer
    Elise Bauer

    When done, transfer the onions and bell peppers into a large gratin pan or casserole dish.

  3. Slice the eggplant, zucchini, and tomato:

    While the onions and peppers are cooking, slice the eggplant and zucchini in 1/4-inch thick round slices.

    You'll also want to slice the tomato into 1/4-inch thick slices, but depending on how big your tomato is, you may need to cut the tomato in half or in quarters first.

    All of the sliced vegetable pieces should be about the same size to make it easier to layer them in an attractive manner.

  4. Layer the sliced vegetables, add the garlic:

    Spread the cooked onions and bell peppers in an even layer at the bottom of the gratin dish. Place the mashed garlic on top of the onions and peppers.

    Arrange the slices of the eggplant, zucchini, and tomato on top of the cooked onions and peppers, alternating the vegetables, in an attractive pattern, stacking and fanning them across the surface of the dish.

    Elise Bauer
    Elise Bauer
  5. Top with salt, parsley, cheeses, and olive oil:

    Sprinkle with salt and parsley. Top with provolone and Parmesan cheeses.

    Drizzle the remaining tablespoon of olive oil around the perimeter, where the vegetables meet the side of the dish.

    Elise Bauer
  6. Bake, then broil to finish:

    Cover with foil (it helps to grease the underside of the foil with a little olive oil so that the cheese as it melts does not stick to the foil).

    Bake for 40 minutes. Remove the foil. Turn on the broiler and broil for 5 minutes or until nicely browned.

Nutrition Facts (per serving)
114 Calories
8g Fat
9g Carbs
4g Protein
Show Full Nutrition Label Hide Full Nutrition Label
Nutrition Facts
Servings: 6 to 8
Amount per serving
Calories 114
% Daily Value*
Total Fat 8g 10%
Saturated Fat 2g 12%
Cholesterol 7mg 2%
Sodium 503mg 22%
Total Carbohydrate 9g 3%
Dietary Fiber 2g 8%
Total Sugars 4g
Protein 4g
Vitamin C 36mg 179%
Calcium 96mg 7%
Iron 1mg 4%
Potassium 295mg 6%
*The % Daily Value (DV) tells you how much a nutrient in a food serving contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.
Nutrition information is calculated using an ingredient database and should be considered an estimate. In cases where multiple ingredient alternatives are given, the first listed is calculated for nutrition. Garnishes and optional ingredients are not included.