Summer Squash Tomato Gratin

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This delicious yellow squash and tomato gratin is easy to make and results in a wonderful side dish with a crispy, cheesy topping.

You can use summer squash or zucchini for this recipe, along with tomatoes, bell pepper, and shallots.

This recipe serves 6 as a side dish, but I love to eat it as a main course as well!

Why You'll Love Tomato Squash Casserole

This delicious squash, tomato, and bell pepper dish is bursting with summer flavors and makes for a delicious side dish or lighter main course!

The panko and cheese toast nicely and combine to create a savory crust for the vegetables.

This recipe is a great dish to take to a potluck or picnic.

Ingredients You'll Need

Summer Squash - You'll need two yellow squash (also called straight neck squash, or yellow zucchini) for this recipe. If you'd prefer, you can also use two zucchini squash.

Tomatoes - You'll need three medium or two large tomatoes. I used heirloom tomatoes because I love their flavor, but you can also use beefsteak, Roma, or any other tomato type you have on hand.

Bell Pepper - You'll need one bell pepper for this recipe. I used an orange bell pepper (for the taste and color), but you can also use orange or yellow. I would not recommend using a green bell pepper.

Shallots - You'll need two medium-sized shallots for this recipe. If you can't find shallots, you can also use half a red onion.

Gruyere - You'll need 1 cup of shredded gruyere cheese.

Panko - You'll need ½ cup of Panko breadcrumbs for this recipe. You can use regular breadcrumbs, but I find them denser and less easy to crisp.

Seasonings - You'll need 1 teaspoon of Italian seasoning for this recipe. Make your own blend using our Italian seasoning recipe. You'll also need 1 teaspoon of kosher salt and ½ teaspoon ground black pepper.

Tips for Choosing the Best Produce

When choosing the best summer squash, you'll want to look for size, firmness, and blemish-free skin. Squash that have grown too large will be lacking in flavor and will have a dry texture. Squash should have a firm texture with no bruising and skin that isn't pockmarked.

The best tomatoes will be firm and heavy for their size. They shouldn't have any bruises, holes, or tears. Great tomatoes will also smell very aromatic!

Finally, the best bell peppers will be brightly colored, firm, and without any visible bruising or marks.

More Summer Side Dish Recipes to Try

Try some of our other seasonal favorites that feature tomatoes, squash, and bell peppers.

• Easy Tomato Salad with Tarragon Pesto - this gorgeous tomato salad is topped with a tangy and unusual pesto.
• Shaved Zucchini Salad Recipe - this side dish is one of our all-time favorites - perfectly ribboned zucchini topped with cheese and pine nuts.
• Black Bean Salad with Bell Peppers - this easy chopped salad with black beans is a summer classic.

Tips for Making this Recipe

Cooking Tips - If your panko is not browning, but the vegetables are roasted, turn on your broiler for one or two minutes to crisp the topping.

Specialty Ingredients - This recipe calls for Italian seasoning. You can make your own blend with our Italian seasoning recipe.

Recommended Tools - You'll need a large baking dish (9x13 or similar sized) for this recipe. Here's the one I use.

Storing Tips - You can save this dish in the refrigerator for up to 4 days, but I think it's best the day you make it (the topping is crispier straight out of the oven). I would highly recommend you reheat it in the oven.

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