Rosemary & Parmesan Squash Casserole

  • Author: Lisa @ This Pilgrim Life
  • Prep Time: 10 minutes
  • Cook Time: 40 minutes
  • Total Time: 50 minutes
  • Yield: 4-6 servings 1x
  • Category: Side dish



  • 1 tablespoon ghee
  • 1 cup diced yellow onion
  • 3 medium yellow squash, cut into 1/2” half moons
  • 1 tsp kosher salt
  • 1 1/2 tsp fresh chopped rosemary, divided
  • 1 egg
  • 1/2 cup mayonnaise
  • 1/2 cup shredded cheddar cheese
  • 3/4 cup shredded Parmesan cheese, divided
  • 1 cup crushed croutons


  1. Melt the ghee in a 10″ skillet over medium heat. Add the diced onion and the squash, season with the salt and 1 teaspoon of rosemary. Stir to mix together the vegetables with the ghee and seasoning. Let the mixture cook, stirring a couple of times, for about 20-25 minutes, until the squash is fork tender. (You don’t want the squash to overcook and become mushy in the oven).
  2. Preheat the oven to 350 degrees after the squash mixture has been cooking for about 10 minutes.
  3. Put the croutons in a sandwich bag and smash with the bottom of a measuring cup or spoon. Stir together the egg, mayo, cheddar cheese, and a half cup of the parmesan cheese in a glass measuring cup. Remove the skillet from the heat, and stir in the egg mixture. Toss well to coat. You can cook the casserole in the skillet, or transfer to a baking dish. If cooking in a baking dish, transfer the squash mixture now.
  4. Top the squash casserole with the crushed croutons, then a 1/4 cup of shredded Parmesan, and finally with a half teaspoon of rosemary. Bake for 15 minutes in preheated oven.
  5. Serve immediately, or keep warm until ready to serve*.


*If you want to prep the casserole ahead of time, complete the first step and then keep the casserole in the fridge until you’re ready to bake. Wait to add the topping until just before baking.