Picture a casserole dish emerging from the oven, its golden, crackly topping giving way to pockets of velvety butternut orange and ribbons of emerald spinach.
Steam carries a cozy aroma of buttered onions, nutmeg, and thyme—the kind of scent that makes a kitchen feel like a hug.
I come back to this Butternut Squash Spinach Casserole whenever I need comfort that’s wholesome, colorful, and genuinely satisfying.
It’s the kind of recipe that steadies a busy weeknight, anchors a Sunday supper, or slips easily onto a holiday table without fuss.
One cold evening, this dish rescued dinner when plans fell apart—its creamy ricotta custard and roasted squash felt special yet required only pantry staples and a single baking dish.
It’s hearty without heaviness, familiar but fresh, and wonderfully make-ahead friendly, so you can bake when life allows and serve when everyone’s hungry.
Ready? Let’s cook!
Why You’ll Love It
- Delivers cozy, savory-sweet flavor with warming spices
- Packs nutritious veggies, protein-rich dairy, and fiber
- Assembles easily with simple, accessible ingredients
- Bakes to a golden, crunchy, cheesy topping
- Meal-prep friendly; reheats beautifully for leftovers
Ingredients
- 2 lb butternut squash, peeled, seeded, cubed 1-inch — roast just to fork-tender (choose a firm, heavy squash)
- 1 tbsp olive oil, extra-virgin — for roasting squash (use fruity, fresh oil)
- 1 tsp kosher salt, divided — seasons in layers (Diamond Crystal preferred)
- 1/2 tsp black pepper, divided — freshly ground boosts aroma (medium grind)
- 1 tbsp unsalted butter — for sautéing aromatics (high-quality dairy)
- 1 small yellow onion, diced — sweet base flavor (look for firm, no sprouts)
- 3 cloves garlic, minced — fragrant backbone (use fresh, not pre-minced)
- 5 oz fresh baby spinach, roughly chopped — wilts quickly (bright, perky leaves)
- 1 cup whole-milk ricotta cheese — creamy binder (drain if watery)
- 1/2 cup sour cream or Greek yogurt — tang and moisture (full-fat preferred)
- 2 large eggs, lightly beaten — set the casserole (fresh, pasture-raised if possible)
- 1/2 cup milk, whole or 2% — loosens the custard (avoid skim)
- 1/2 tsp dried thyme — earthy herb note (rub to release oils)
- 1/4 tsp ground nutmeg — warms the squash (freshly grated if possible)
- 1/4 tsp red pepper flakes, optional — gentle heat (adjust to taste)
- 1 cup shredded mozzarella cheese, divided — melt and stretch (low-moisture, part-skim)
- 1/2 cup grated Parmesan cheese, divided — savory umami (Parmigiano Reggiano if possible)
- 1/2 cup panko breadcrumbs — crisp topping (Japanese-style for light crunch)
- 1 tbsp olive oil — for topping (helps panko brown)
- 1 tbsp fresh parsley, chopped — bright garnish (flat-leaf for best flavor)
Step-by-Step Method
Preheat and Prep the Dish
Preheat the oven to 400°F. Lightly grease a 9×13-inch baking dish. Peel, seed, and cube the butternut squash into 1-inch pieces. Gather all equipment and ingredients. Set out a large skillet, mixing bowl, whisk, saucepan, and foil. This mise en place speeds cooking and prevents overcooking the squash later.
Roast the Butternut Squash
Toss squash with 1 tablespoon olive oil, 1/2 teaspoon kosher salt, and 1/4 teaspoon black pepper. Spread in an even layer in the prepared baking dish. Roast for 20 to 25 minutes until just fork-tender. Avoid over-roasting to keep cubes intact. Remove from the oven and set aside.
Lower the oven temperature to 375°F later.
Sauté the Aromatics
Melt 1 tablespoon unsalted butter in a large skillet over medium heat. Add diced yellow onion with a pinch of salt. Cook for about 5 minutes, stirring occasionally, until translucent and soft. Avoid browning the onions. This builds a sweet base flavor that complements the creamy ricotta mixture in the casserole.
Wilt the Spinach
Stir in minced garlic and cook for 30 seconds until fragrant. Add the roughly chopped baby spinach. Cook 2 to 3 minutes, stirring, until wilted and bright green. Remove the skillet from heat and let the mixture cool slightly. Cooling prevents the hot vegetables from scrambling the eggs in the dairy mixture later.
Whisk the Creamy Base
In a large mixing bowl, whisk ricotta, sour cream or Greek yogurt, lightly beaten eggs, and milk. Add dried thyme, ground nutmeg, remaining 1/2 teaspoon salt, remaining 1/4 teaspoon pepper, and optional red pepper flakes. Whisk until smooth and well combined. This creates a custardy binder that holds the casserole together.
Fold in Veggies and Cheeses
Gently fold the roasted squash and the cooled spinach-onion-garlic mixture into the ricotta base. Add 1/2 cup shredded mozzarella and 1/4 cup grated Parmesan. Mix carefully to avoid breaking the squash cubes. Make certain even distribution for balanced bites. Taste and adjust seasoning if needed, keeping salt mindful due to cheeses.
Assemble the Casserole
Reduce the oven temperature to 375°F. Transfer the mixture into the greased baking dish, smoothing the top with a spoon or spatula. Level the surface for even baking and browning. Tap the dish gently on the counter to remove air pockets. Prepare the crumb topping while the casserole settles briefly.
Mix the Crunchy Topping
In a small bowl, combine panko breadcrumbs, remaining 1/2 cup mozzarella, remaining 1/4 cup Parmesan, and 1 tablespoon olive oil. Toss until evenly moistened and clumpy. The oil helps achieve crisp, golden crumbs. Sprinkle the mixture evenly over the casserole, covering the surface without packing it down.
Bake Covered, Then Uncover
Cover the dish loosely with aluminum foil, tenting to prevent sticking. Bake at 375°F for 20 minutes. Remove the foil and continue baking 10 to 15 minutes more, until bubbling at the edges and the top is golden. Rotate the dish if browning unevenly. Avoid overbaking to keep the interior creamy.
Rest, Garnish, and Serve
Remove the casserole from the oven and let it rest for 10 minutes. This allows the custard to set for clean slices. Garnish with chopped fresh parsley for color and freshness. Serve warm as a main dish. Store leftovers refrigerated 3 to 4 days and reheat covered at 350°F until heated through.
Ingredient Swaps
- Dairy-free: use plant-based ricotta (or silken tofu blended with lemon and salt), vegan sour cream/yogurt, and dairy-free mozzarella/Parmesan.
- Lighter: swap sour cream for plain Greek yogurt; use part-skim ricotta and reduced-fat mozzarella.
- Higher protein: replace ricotta with cottage cheese (blended for smoothness) or add cooked chicken/white beans.
- Gluten-free: replace panko with GF breadcrumbs or crushed GF cornflakes/almonds.
- Budget/availability: sub butternut with acorn, kabocha, or sweet potatoes; use frozen spinach (well-drained) instead of fresh.
- Herb/spice swaps: sage or rosemary for thyme; cinnamon or pumpkin pie spice (pinch) for nutmeg.
- Cheeses: mozzarella → provolone/monterey jack; Parmesan → pecorino/Grana Padano.
You Must Know
Doneness • If the squash looks too soft after roasting, pull it when a fork meets slight resistance at the edges but the center still feels firm (about 20–22 minutes); this keeps cubes intact so they don’t collapse into the custard.
Troubleshoot • When the filling seems loose before going in the oven, stir in 1–2 tablespoons extra Parmesan or 2 tablespoons panko; they bind excess moisture so the center sets by the 10-minute rest.
Flavor Boost • For deeper squash sweetness, toss cubes with 1 teaspoon maple syrup and an extra pinch of salt before roasting; you should see light caramelized spots and smell toffee notes by minute 22–25.
Swap • To reduce dairy richness without losing body, replace sour cream with Greek yogurt and use part-skim ricotta; add 1 extra egg if the mix feels thin, aiming for a thick, pourable custard that ribbons off a spoon.
Scale • For 8–10 servings in a 9×13 plus a small loaf pan, increase all ingredients by 1.5x and extend covered oven time by 5–10 minutes; the center should jiggle slightly but not wave when nudged.
Serving Tips
- Serve with a crisp green salad and lemon vinaigrette to balance richness.
- Pair alongside roasted chicken or grilled sausage for a heartier plate.
- Add brightness with a dollop of herbed yogurt or pesto drizzle.
- Plate in warmed bowls; finish with extra Parmesan and fresh parsley.
- Offer crusty bread to scoop up creamy, cheesy edges.
Storage & Make-Ahead
Make ahead: Assemble casserole up to 24 hours in advance; cover and refrigerate, then bake adding 10–15 minutes if cold.
Storage: Refrigerate leftovers in an airtight container 3–4 days; reheat covered at 350°F until warmed through.
Freezing: Freezes well (unbaked or baked) up to 2 months; thaw overnight before baking/reheating.
Reheating
Reheat gently: microwave covered at 50–60% power in 60–90‑second bursts.
Oven at 325°F covered 15–20 minutes.
Or stovetop low heat with a splash of milk, stirring occasionally to prevent drying.
Thanksgiving Potluck Favorite
Often the first dish I volunteer to bring, this butternut squash spinach casserole arrives warm and fragrant, its golden crust crackling as I lift the foil.
I set it among the turkey, glistening beans, and braided rolls, and watch spoons reach in before anyone asks who made it.
Sweet squash, silky spinach, and ricotta bake into a custardy middle, while mozzarella-Parmesan panko turns crisp and toasty on top.
I prep it the day before, assemble in a 9×13, and bake it off just before I head out so it travels hot.
It holds beautifully—sliceable, not soupy—thanks to well-roasted squash and well-drained greens.
Want a crowd-pleaser twist? Add nutmeg’s whisper, a pinch of red pepper flakes, and a shower of parsley right before serving.
Final Thoughts
Ready to dig in? Give this cozy casserole a try as written, or tweak it with cottage cheese, sage, or a protein boost—then let me know your favorite spin!
Frequently Asked Questions
Can I Freeze the Casserole Before Baking?
Yes—you can. I assemble it, cool completely, wrap snugly in plastic and foil, then freeze. Bake from frozen at 375°F, covered, adding 20–30 minutes, uncover to crisp the topping. You’ll open the oven to golden, bubbling comfort.
How Do I Make This Casserole Gluten-Free?
Use certified gluten-free panko or crushed GF crackers, double-check spices and dairy labels, and skip any wheat thickeners. I’ll tuck it in the oven; you’ll hear a buttery crackle and taste autumn cozy, worry-free.
What Wine Pairs Best With This Dish?
I’d pour a lightly oaked Chardonnay or Viognier—silky, with stone-fruit warmth—to hug the creamy richness. If you prefer red, I’d choose Pinot Noir: bright cherry, gentle earth, seamless with herbs and sweetness, cozy by candlelight.
Can I Make It in a Slow Cooker?
Yes—you can. I’d sauté the aromatics, then layer squash, spinach mixture, and cheeses in a slow cooker. Cook on low 4–5 hours, uncover last 30 minutes, then broil the topping separately for golden crunch.
How Can I Scale the Recipe for 12 People?
Double everything for 12. I’ll use two 9x13s or one deep roasting pan, roast squash in batches, combine fillings, then bake a bit longer—watch for bubbling edges and golden top. Let it rest, then serve.
Butternut Squash Spinach Casserole
Equipment
- 1 9×13 inch baking dish
- 1 large skillet
- 1 Medium saucepan
- 1 large mixing bowl
- 1 Whisk
- 1 Chef's knife
- 1 Cutting board
- 1 vegetable peeler
- 1 Wooden spoon
- 1 measuring cup set
- 1 measuring spoon set
- 1 aluminum foil sheet
Ingredients
- 2 pound butternut squash peeled, seeded, and cubed 1-inch
- 1 tablespoon olive oil extra-virgin
- 1 teaspoon kosher salt divided
- 1/2 teaspoon black pepper divided
- 1 tablespoon unsalted butter
- 1 small yellow onion diced
- 3 clove garlic minced
- 5 ounce fresh baby spinach roughly chopped
- 1 cup ricotta cheese whole-milk
- 1/2 cup sour cream or Greek yogurt
- 2 large eggs lightly beaten
- 1/2 cup milk whole or 2%
- 1/2 teaspoon dried thyme
- 1/4 teaspoon ground nutmeg
- 1/4 teaspoon red pepper flakes optional
- 1 cup shredded mozzarella cheese divided
- 1/2 cup grated Parmesan cheese divided
- 1/2 cup panko breadcrumbs
- 1 tablespoon olive oil for topping
- 1 tablespoon fresh parsley chopped, for garnish
Instructions
- Preheat the oven to 400°F and lightly grease the 9×13-inch baking dish.
- Toss the cubed butternut squash with 1 tablespoon olive oil, 1/2 teaspoon salt, and 1/4 teaspoon pepper, spread on the baking dish, and roast for 20 to 25 minutes until just tender.
- While the squash roasts, heat the butter in a large skillet over medium heat, add the onion with a pinch of salt, and cook 5 minutes until translucent.
- Stir in the garlic and cook 30 seconds until fragrant, then add the chopped spinach and cook 2 to 3 minutes until wilted; set aside to cool slightly.
- In a large mixing bowl whisk together ricotta, sour cream, eggs, milk, thyme, nutmeg, remaining 1/2 teaspoon salt, remaining 1/4 teaspoon pepper, and red pepper flakes.
- Fold the roasted squash, sautéed spinach mixture, 1/2 cup mozzarella, and 1/4 cup Parmesan into the ricotta mixture until evenly combined.
- Reduce oven temperature to 375°F and transfer the mixture back into the greased baking dish, smoothing the top.
- In a small bowl combine panko, remaining 1/2 cup mozzarella, remaining 1/4 cup Parmesan, and 1 tablespoon olive oil until crumbly.
- Sprinkle the breadcrumb-cheese mixture evenly over the casserole and cover the dish loosely with foil.
- Bake for 20 minutes covered, then remove foil and bake 10 to 15 minutes more until bubbling at the edges and golden on top.
- Let the casserole rest 10 minutes before garnishing with chopped parsley and serving.
Notes
