Homemade Sweet Potato Zucchini Casserole

I’ve been sneaking vegetables into casseroles for years now, and this one might be my best work yet. Sweet potatoes and zucchini sound like an odd couple, but trust me, they’re made for each other. The sweet potato brings a natural sweetness while the zucchini keeps things light and adds moisture without making the whole dish soggy.

This casserole has saved me on busy weeknights more times than I can count. I can throw it together while helping with homework, pop it in the oven, and dinner is done. Plus, my kids actually eat their vegetables this way, which feels like a small miracle.

Want it as a side dish? Perfect. Need it to be the main event? Add some cheese and breadcrumbs on top and you’re good to go. I’ve served this at potlucks, family dinners, and regular Tuesday nights, and it works every single time.

What Kind of Sweet Potatoes Should I Use?

For this casserole, you’ll want to grab medium-sized sweet potatoes that are firm to the touch without any soft spots or sprouting. The orange-fleshed varieties (sometimes labeled as yams in grocery stores) work perfectly here since they hold their shape well when baked and have a naturally sweet flavor that balances the savory sausage and tomatoes. When you’re prepping them, aim to slice your sweet potatoes into thin, even circles – about 1/4 inch thick – so they cook through properly and create nice layers in your casserole. If your sweet potatoes are on the larger side, you might only need one and a half instead of two full ones.

Options for Substitutions

This casserole is pretty forgiving when it comes to swapping ingredients:

• Ground turkey sausage: You can easily swap this with ground beef, ground chicken, or regular pork sausage. If using unseasoned ground meat, add a pinch of fennel seeds and red pepper flakes to mimic that sausage flavor.
• Zucchini: Yellow squash works just as well and has a similar texture. You can also use eggplant, though you’ll want to salt it first and let it sit for 15 minutes to remove excess moisture.
• Sweet potatoes: Regular white potatoes or butternut squash can step in here. Keep the slicing thin so they cook through properly in the casserole.
• Mozzarella cheese: Any melting cheese works – try provolone, monterey jack, or regular mozzarella if you’re not worried about the fat content. Cheddar will give you a sharper flavor.
• Fresh parsley: Dried parsley (use 2 teaspoons) or fresh basil make good substitutes. You can also skip the garnish entirely if you don’t have any on hand.
• Italian seasoning: Make your own blend with equal parts dried basil, oregano, and thyme, or just use whatever dried herbs you have in your pantry.

Watch Out for These Mistakes While Cooking

The biggest mistake when making this casserole is slicing your sweet potatoes too thick, which can leave them undercooked and crunchy – aim for slices about 1/8 inch thick using a mandoline or sharp knife for even cooking.

Another common error is not draining the excess liquid from your zucchini and diced tomatoes, which can turn your casserole watery instead of nicely set, so press the zucchini with paper towels after cooking and drain the canned tomatoes well.

Don’t skip browning the turkey sausage properly before layering – it should be fully cooked with no pink remaining and have some caramelization, which adds flavor to the entire dish.

Finally, resist the urge to skip covering the casserole with foil for the first part of baking, as this helps the sweet potatoes steam and cook through before you add the cheese and finish uncovered for that golden top.

What to Serve With Sweet Potato Zucchini Casserole?

This casserole is pretty hearty on its own, but I love serving it with a simple side salad dressed with olive oil and lemon juice to balance out the richness. A crusty baguette or some garlic bread on the side is perfect for anyone who wants a little extra something to round out their plate. If you’re feeding a crowd, roasted green beans or sautéed spinach make great veggie additions that won’t compete with the flavors in the casserole. You could also serve it alongside some crusty bread for soaking up any extra tomato sauce at the bottom of your bowl.

Storage Instructions

Store: This casserole keeps really well in the fridge for up to 4 days in an airtight container. It’s one of those dishes that actually tastes better the next day once all the flavors have had time to hang out together. I like to portion it out into individual containers for easy grab-and-go lunches throughout the week.

Freeze: You can freeze this casserole either before or after baking. If freezing unbaked, cover it tightly with plastic wrap and foil, and it’ll keep for up to 3 months. Already baked? Let it cool completely, then freeze in portions or as a whole for the same amount of time.

Reheat: Warm up individual portions in the microwave for 2-3 minutes, or reheat the whole casserole covered with foil in a 350°F oven for about 20-25 minutes until heated through. If reheating from frozen, add an extra 10-15 minutes to the oven time.

Preparation Time	15-20 minutes
Cooking Time	25-30 minutes
Total Time	40-50 minutes
Level of Difficulty	Medium

Estimated Nutrition

Estimated nutrition for the whole recipe (without optional ingredients):

• Calories: 850-950
• Protein: 60-70 g
• Fat: 25-30 g
• Carbohydrates: 90-110 g

Ingredients

For the filling:

• 1 tbsp olive oil (or any neutral oil like canola)
• 1 lb ground turkey sausage (Italian seasoning preferred)
• 2 garlic cloves (freshly minced)
• 15 oz canned diced tomatoes (I use San Marzano)
• 1 tbsp Italian seasoning
• 1/2 cup yellow onion (finely chopped into 1/4-inch pieces)
• 2 zucchini (diced into 1/2-inch pieces)
• 2 tbsp tomato paste (adds rich, concentrated flavor)

For the base:

• 2 sweet potatoes (scrubbed and sliced into 1/8-inch rounds)

For the topping:

• 1/2 cup fat-free shredded mozzarella cheese (optional but recommended for melting and richness)
• 2 tbsp grated parmesan cheese
• 2 tbsp fresh parsley (finely chopped, for garnish)

Step 1: Prepare Ingredients and Preheat Oven

• 2 sweet potatoes
• 2 zucchini
• 1/2 cup yellow onion
• 2 garlic cloves

Preheat your oven to 350°F and spray a 9×13-inch casserole dish lightly with cooking spray.

While the oven heats, prepare your mise en place: dice the zucchini into 1/2-inch pieces, finely chop the yellow onion into 1/4-inch pieces, mince the garlic cloves, and scrub the sweet potatoes.

Slice the sweet potatoes into thin 1/8-inch rounds using a mandoline or sharp knife—uniform thickness ensures even cooking.

I like to soak the potato slices in cold water for a few minutes to remove excess starch, which helps them cook more evenly and prevents them from sticking together.

Step 2: Build the Sauce Base with Aromatics

• 1 tbsp olive oil
• 1/2 cup yellow onion
• 2 garlic cloves
• 2 zucchini

Heat the olive oil in a large skillet over medium-high heat.

Once shimmering, add the chopped onion and cook for 2 minutes until it begins to soften and become translucent.

Add the minced garlic and diced zucchini, stirring frequently, and cook for another 2 minutes to release the aromatics and allow the zucchini to release some of its moisture.

This foundational step builds layers of flavor that will infuse the entire casserole.

Step 3: Brown the Sausage and Develop the Sauce

• 1 lb ground turkey sausage
• 2 tbsp tomato paste
• 15 oz canned diced tomatoes
• 1 tbsp Italian seasoning

Add the ground turkey sausage to the skillet with the cooked vegetables, breaking it apart with a wooden spoon as it cooks over medium-high heat.

Cook for 4-5 minutes, stirring occasionally, until the sausage is no longer pink and has begun to brown slightly.

Stir in the tomato paste and cook for 1-2 minutes to caramelize it slightly and deepen its flavor.

Pour in the canned diced tomatoes with their juice, add the Italian seasoning, and stir well to combine.

Reduce heat to medium and simmer for 5-7 minutes until the sauce thickens slightly and the flavors meld together.

I find that letting the sauce simmer rather than rushing this step makes a huge difference in the final flavor—the tomato paste becomes rich and the sausage flavors really shine through.

Step 4: Layer and Assemble the Casserole

• sweet potato slices from Step 1
• sausage mixture from Step 3

Drain the sweet potato slices if you soaked them (this step removes excess starch that can make the dish watery).

Arrange the sweet potato slices in an even layer across the bottom of your prepared casserole dish, slightly overlapping them for a compact fit.

Spread the sausage mixture from Step 3 evenly over the sweet potatoes, using a spatula to distribute it uniformly.

Make sure the sauce coats all the potatoes so they’ll cook evenly and absorb the flavors.

Step 5: Top with Cheese and Bake

• 2 tbsp grated parmesan cheese
• 1/2 cup fat-free shredded mozzarella cheese

Sprinkle the grated parmesan cheese evenly over the sausage layer, followed by the shredded mozzarella cheese.

The combination of parmesan for sharpness and mozzarella for melting creates a cohesive, flavorful top.

Place the casserole in the preheated 350°F oven and bake for 25-30 minutes until the sweet potatoes are completely tender when pierced with a fork and the cheese on top is melted and lightly golden.

The sweet potatoes will be the best indicator of doneness since they’re the thickest component.

Step 6: Finish and Serve

• 2 tbsp fresh parsley

Remove the casserole from the oven and let it rest for 3-5 minutes before serving.

This short rest allows the layers to set slightly and makes serving cleaner.

Sprinkle the fresh chopped parsley over the top as a bright, fresh garnish that adds visual appeal and a hint of herbaceous freshness to balance the rich, savory casserole.