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+ servings

Summer Squash Gratin

Servings 8 servings
Author Melissa Sperka


  • 1 1/2 lb zucchini 1/4" slices
  • 1 1/2 lb yellow squash 1/4" slices
  • 1 medium sweet onion small dice
  • 1/2 cup butter plus 2 Tbsp divided
  • 1 Tbsp Dijon mustard
  • 1/3 cup all purpose flour
  • 1 tsp salt
  • 1/2 tsp white or black pepper
  • 1/2 tsp garlic powder
  • 3 cups milk
  • 3 cups shredded sharp cheddar cheese divided [white or yellow]
  • 1 sleeve buttery round crackers crushed [I used Ritz Roasted Vegetable]


  • Preheat the oven to 350°F. Spritz an 9 x 9 deep dish baking dish or an 8 x 12 inch oblong dish with cooking spray.
  • Steam the sliced zucchini and yellow squash until fork tender, around 7-8 minutes. Drain and cool slightly.
  • In a heavy bottomed saucepan, cook the diced onion in 1/2 cup of butter.
  • Cook over medium high heat until soft, around 3 minutes. Add the Dijon mustard, all purpose flour, salt, pepper and garlic powder. Whisk over medium heat until combined.
  • Gradually add the milk, whisking constantly. Bring to a boil, then lower the heat and gently bubble for 5 minutes until thickened.
  • Add 1 cup of shredded cheese to the sauce and stir until melted.
  • To assemble: Layer half of the steamed squash into the bottom of the dish. Season lightly with salt and black pepper to your taste. Cover with 1/2 of the sauce and sprinkle with 1 cup of shredded cheese.
  • Repeat layers: Last layer of squash, salt & black pepper, remaining sauce, then ending with 1 cup of shredded cheese.
  • Melt 2 Tbsp of butter and toss with the cracker crumbs. Spread on top.
  • Bake for 35-40 minutes until golden and bubbly.