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Potato and Yellow Squash Au Gratin

sprinkling basil on top of potato and yellow squash au gratin

A remake of the classic potatoes au gratin. This potato and yellow squash au gratin is just as delicious as the classic version and full of cheesy goodness.

When I think of au gratin, I think of the boxed stuff. I used to coupon and that was one item, especially in the fall, that you could always get for just a few cents with coupons. Yum, dehydrated potato slices and powdered dairy magic. Probably (or definitely) not healthy at all. I wanted to remake this classic side dish and add yellow squash to bump up the healthiness. Also, because I wanted to do something other than just roast the yellow squash. Potato and yellow squash au gratin is a great side dish to serve with many different meals.

up close potato and yellow squash au gratin

Just because I’m curious, I had to look up what “au gratin” means because I’m fairly certain it has nothing to do with potatoes. According to Google, it means “sprinkled with breadcrumbs or grated cheese, or both, and browned”. You’re welcome, now let’s top everything with cheese!

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Potato and Yellow Squash Au Gratin

Cheesy Au Gratin made with potatoes and yellow squash.
Prep Time 25 minutes
Cook Time 1 hour
Course Side Dish
Cuisine French
Servings 6 Servings
Calories 304 kcal


  • 1 Tablespoon olive oil
  • 1 small onion, chopped
  • 3 Tablespoons butter
  • 3 Tablespoons flour
  • 2 cups whole milk
  • 1 cup cheddar cheese, shredded
  • salt & pepper
  • 3 medium Russet potatoes
  • 3 yellow squash


  • Preheat oven to 350°F and grease a pie pan or 8 x 8 inch pan.
  • Add butter to a large skillet and melt. Whisk in flour and season with salt and pepper. Slowly add milk, ½ cup at a time while whisking. Cook until thickened, about 2 minutes. Stir in cheese until melted.
  • Peel potatoes and slice very thin. Put potato slices right into the sauce as they are peeled so they don’t turn brown. Slice the yellow squash very thin and put into the sauce. Stir to combine and pour into prepared pan.
  • Cover with foil and bake for 1 hour. Uncover and check if potatoes are tender. Depending on how thin the potatoes are sliced it might need more time to bake, another 10-15 minutes. Brown the top under the broiler when potatoes are tender. You can sprinkle with more shredded cheese before browning if you want.
Keyword Cheese, Potatoes, Squash