Zucchini Squash Gratin Recipe

5 / 5 ( 1 Review )
No Comments Jump to Recipe

Zucchini Gratin Casserole Side Dish

Got a lot of zucchini? This is an awesome side dish recipe to use up a few yellow squash and zucchini from the garden.

zucchini gratin recipe

This zucchini gratin has a great texture and flavor. It is a like a healthy comfort food and would be a nice side dish all year round, but definitely when summer squash is in season.

zucchini gratin with onions

First, you want to cook down a bunch of sliced onion. Use about 1 pound of onion, which is usually about 1 1/2 medium yellow onions. Peel off the outer layer, cut each in half, then slice them up.

zucchini gratin sliced squash

If you find yourself slicing zucchini and squash a lot, then you really should get yourself a mandoline slicer. The slices are all about the same thickness and you can get it done fast! It only takes a minute or two to slice up all 4 of the squash for this recipe! Very handy, especially for a recipe like this one.

zucchini gratin with squash

You will need to use a large skillet or saute pan, 12-inches or larger, for all of the onion, zucchini, and yellow squash in there. If you have one with a lid, even better because you will need to cover the pan for part of the cooking time.

zucchini gratin topped with parmesan and Italian bread crumbs

Just dump the tender zucchini, onion, and sauce into a smallish baking dish and top with the grated cheese and bread crumbs. I usually use freshly grated Parmesan with the Italian bread crumbs. So good!

To make this TERRAfit-friendly, use whole grain flour and whole grain bread crumbs.

This recipe is from Our Best Bites and Ina Garten.

Swissmar Borner V-1001 V-Slicer Plus Mandoline

A good mandoline can quickly, uniformly, and safely slice and julienne vegetables and fruits. It can also shred cabbage and neatly dice potatoes, tomatoes, and onions.

I just got a Swissmar Borner mandoline for myself because it has a ton of great ratings. I used it for this recipe and so far, so good! I also ordered some cut resistant gloves.

Zucchini Squash Gratin Recipe

Got a lot of zucchini? This is an awesome side dish recipe to use up a few yellow squash and zucchini from the garden.
5 / 5 ( 1 Review )
Print Pin Rate
Prep Time: 10 minutes
Cook Time: 1 hour
Total Time: 1 hour 10 minutes
Serves: 6
Adjust Servings: 6


  • 5 tablespoons butter
  • 1 pound yellow onions cut in 1/2 and sliced
  • 2 pounds zucchini and/or yellow squash sliced 1/4-inch thick (about 4)
  • ¾ teaspoon kosher salt use 1/2 teaspoon if using table salt
  • 1 teaspoon black pepper
  • ¼ teaspoon ground nutmeg
  • 2 cloves garlic finely minced or pressed
  • 2 tablespoons all-purpose flour
  • 1 cup milk
  • 6 tablespoons Italian style bread crumbs
  • ¾ cup grated Parmesan or Gruyere
  • olive oil


  • Preheat the oven to 400°F/200°C
  • Melt the butter in a large saute pan and cook the onions over low heat for 20 minutes, or until tender but not browned.
  • As the onions are cooking, stir them occasionally and work on prepping the other ingredients.
  • Add the zucchini and cook, covered, for 8-10 minutes, or until tender.
  • Add the salt, pepper, and nutmeg and garlic and cook uncovered for 5 more minutes, stirring often.
  • Whisk flour into the milk and add to pan, turning up heat slightly just until milk heats and starts bubbling.
  • Then cook over low heat for a few minutes, until it thickens and makes a sauce.
  • Pour the zucchini mixture, and all the sauce into an 8 by 10-inch baking dish (or something close to that).
  • Combine the bread crumbs and Parmesan in a small bowl.
  • Sprinkle on top of the zucchini mixture.
  • Drizzle a little olive oil over the top (place your finger over the opening of the bottle to make it easier to just drizzle a little) and bake for 20 minutes, or until bubbly and browned. Cool for a few minutes before serving.

Recipe Notes

If doubling recipe, use a 9×13 (or similar) pan.


Calories: 268kcal | Carbohydrates: 24g | Protein: 11g | Fat: 16g | Sodium: 732mg | Fiber: 3g | Sugar: 10g

Ingredients: Zucchini
Meal Type: Side Dish, Clean Eating
Categories: Healthy

Leave a Review/Reply

Want to see your picture by your comment? Get your custom avatar by registering for free at Gravatar.

Your email address will not be published.

Recipe Rating