Zucchini stuffing casserole is a comforting, savory side dish that's perfect for your next holiday dinner. Layers of creamy mushroom zucchini filling and homemade stuffing are baked to perfection in the oven.
While searching for a recipe for zucchini stuffing casserole, I couldn't find a single one made entirely from scratch. They all included boxed or canned ingredients. While these ingredients can be great time-savers, I love cooking from scratch when I have the chance. I saw this as a great opportunity to develop a brand new recipe!
Zucchini stuffing casserole, from the stuffing to the creamy mushroom sauce, is made entirely from scratch. The stuffing adds some heft to the filling and doubles as a crunchy layer on top. Worried about soggy zucchini? This zucchini filling is flavorful, creamy, and maintains its firm texture in the oven without getting soggy or wet.
Serve zucchini stuffing casserole at your next family dinner or holiday meal. It's perfect for Thanksgiving and Christmas!
Ingredients and substitutions
- Butter - Unsalted butter can be substituted with salted butter if desired (you'll want to cut the listed salt in half).
- Onion - Adds flavor to the stuffing layers. I do not recommend omitting it.
- Celery - Adds peppery flavor to the stuffing layers. I do not recommend omitting it.
- Stuffing seasoning - Sage, salt, and pepper add flavor to the stuffing layers. Sage can also be substituted with poultry seasoning if desired.
- Bread cubes - You'll need about 6 cups, or ½ pound (before drying), of crusty bread cubes for this recipe. I used a loaf of French bread, but sourdough bread, Italian bread, or any sturdy sandwich bread will work. Avoid using overly soft and fluffy white sandwich bread - it doesn't hold up well in the recipe.
- Mushrooms - Mushrooms add earthy, savory flavor and help mimic the flavor of a cream of mushroom soup.
- Broth - Chicken broth or vegetable broth works in this recipe.
- Milk - I recommend whole milk for a creamy sauce. Using lower fat milks will result in a thin sauce.
- Flour - All-purpose flour is used, along with the listed butter, to create a roux, which thickens the creamy mushroom sauce. This ingredient cannot be omitted.
- Sauce seasoning - Salt, pepper and thyme are added to the mushroom sauce for a mild, savory flavor.
- Zucchini - You'll need about 2 pounds of thick sliced zucchini for this recipe. This equals about 4 medium zucchini.
Tips and tricks
Dry bread cubes beforehand - Bread can be dried out 2 to 3 days before preparing your casserole to save time. Using a serrated knife, slice bread into ½ inch cubes. Spread into a single layer on a sheet pan and cover with a tea towel. Allow bread to dry out for 1 to 2 days, or until crunchy, then store in a sealed container until ready to use. To dry out quicky in the oven, preheat oven to 225 degrees Fahrenheit and bake for about 30 minutes, or until bread cubes are crunchy and dry.
Slice zucchini into thick slices - About ¼ to ⅓ inch slices work best in this recipe. Very thin slices can cook too fast and turn out mushy when overcooked.
Allow mushroom sauce to thicken - When cooking the mushroom sauce, make sure it thickly coats the back of a spoon before removing from the heat. This ensures your casserole doesn't turn out too wet.
For a smooth sauce, use a whisk - After you've made your roux, slowly whisk the broth and milk into the pan and continue whisking until your sauce looks smooth. Whisk frequently throughout cooking to prevent lumps.
Allow casserole to rest before serving - Straight from the oven your casserole will be very hot and the sauce may appear a little thin. Allow it to set for about 20 minutes to cool down and allow the sauce to thicken before serving.
Frequently asked questions
Soggy zucchini is the result of overcooking. Many similar recipes call for par-cooking the zucchini before baking in the oven. This recipe does not require par-cooking because I think it's unnecessary and can easily lead to soggy zucchini. If your zucchini is sliced fairly thick (between ¼ and ⅓ inch), and you're not cooking the casserole longer than directed, the zucchini will come out firm and perfectly cooked - not soggy.
No, there's no need to peel your zucchini for this recipe. If you're using a very large zucchini, it may have tough skin - in this case you may choose to peel it.
Yes, some or all of the zucchini can be substituted with summer squash if desired.
Because of the wet and dry components in this recipe, I recommend preparing and storing the parts separately. Assemble the casserole just before baking for best results. Storing the prepared casserole in the refrigerator will cause the stuffing to get soggy.
Zucchini Stuffing Casserole
- ¼ cup (56 g) unsalted butter
- 1 small onion, chopped
- 2 celery ribs, chopped
- ¾ teaspoon dried sage
- ½ teaspoon salt
- ¼ teaspoon pepper
- 6 cups dried bread cubes, or about ½ pound of crusty bread, sliced into small cubes and dried out*
- ¼ cup (56 g) unsalted butter
- 4 ounces (113 g) button mushrooms, sliced
- 16 ounces (453 g) chicken broth
- 12 ounces (340 g) whole milk
- ¼ cup (30 g) all-purpose flour
- ½ teaspoon dried thyme
- ½ teaspoon salt
- ¼ teaspoon pepper
- 2 pounds (907 g) zucchini, thick sliced, about 4 to 5 medium zucchini
- Preheat oven to 350 degrees Fahrenheit. Lightly grease a 9x13 casserole dish and set aside.
- In a saucepan over medium heat, melt butter. Add onion and celery and cook until softened, about 4 to 5 minutes. Remove from heat and add seasoning. Toss with bread cubes and set aside.
- In a saucepan over medium heat, melt butter. Add mushrooms and cook until lightly browned, about 3 to 4 minutes. Whisk in flour and cook for another minute. Slowly add broth, milk, thyme, salt, and pepper, whisking until smooth. Cook another 3 to 5 minutes, or until thickened slightly (sauce should thickly coat the back of a spoon). Remove from heat and add zucchini, tossing to coat.
Assembly and baking
- Spread half of stuffing mixture into a single layer in the bottom of your casserole dish. Top with entire zucchini filling mixture. Top with remaining stuffing, spread into an even layer.
- Bake for about 40 minutes, or until topping is browned and filling is hot and bubbling throughout.
- Remove from oven and allow to set for 20 minutes before serving.
- * To dry out fresh bread - Preheat oven to 225 degrees Fahrenheit and spread bread cubes into a single layer on a sheet pan. Bake for 30 to 40 minutes, or until dry and crunchy, stirring once halfway through.
- Leftovers will keep for 3 to 4 days in a tightly sealed container in the refrigerator. Stuffing topping will get soft.