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Cheesy Squash Zucchini Casserole Recipe

Cheesy Squash Zucchini Casserole Recipe

Thin-sliced yellow squash and zucchini bake in a creamy, cheesy sauce under a crisp buttery crumb topping. Comforting, golden, and perfect for weeknights or potlucks.
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Prep Time: 20 minutes
Cook Time: 35 minutes
Total Time: 55 minutes
Servings: 8

Ingredients
 

Main Ingredients

  • 1.25 lb yellow squash, thinly sliced
  • 1 lb zucchini, thinly sliced
  • 1.5 tbsp olive oil
  • 1 cup diced onion
  • 1 tsp minced garlic
  • 0.75 cup sour cream
  • 0.25 cup mayonnaise
  • 2 tbsp all-purpose flour
  • 1.5 cup shredded sharp cheddar cheese
  • 0.33 cup grated Parmesan cheese
  • 1 tsp kosher salt
  • 0.5 tsp black pepper
  • 0.5 tsp dried thyme
  • 0.25 tsp red pepper flakes optional
  • 0.75 cup panko breadcrumbs
  • 2 tbsp unsalted butter, melted
  • 2 tbsp chopped fresh parsley for garnish

Instructions

Preparation Steps

  • Preheat oven to 375°F. Grease a 9x13-inch baking dish.
  • Warm olive oil in a large skillet over medium-high heat.
  • Sauté onion until translucent, about 4 minutes. Stir in garlic for 30 seconds.
  • Add squash and zucchini. Cook, stirring, until just tender and most liquid evaporates, 7–9 minutes.
  • Spread vegetables on a towel-lined sheet to release steam. Cool 5 minutes.
  • Whisk sour cream, mayonnaise, flour, salt, pepper, thyme, and red pepper flakes in a large bowl.
  • Fold in 1 cup cheddar and 1/4 cup Parmesan.
  • Add cooled vegetables to the bowl and toss until evenly coated.
  • Scrape mixture into the prepared dish. Sprinkle with remaining cheddar.
  • Combine panko, melted butter, and remaining Parmesan. Scatter evenly over the top.
  • Bake until bubbling and golden, 22–28 minutes. Rest 10 minutes before serving.
  • Garnish with parsley and serve warm.

Notes

Swap the cheddar for pepper jack for a mild kick, or add 1 cup cooked crumbled bacon or rotisserie chicken for extra protein. For a gluten-free topping, use crushed gluten-free crackers or almond meal instead of panko. Refrigerate leftovers in an airtight container up to 3 days; reheat covered at 350°F until warmed through.
This recipe is an original creation inspired by classic Cheesy Squash Zucchini Casserole Recipe flavors. All ingredient ratios and instructions are independently developed.