Name: Tennessee Onions: Cheesy Baked Sweet Onion Casserole Recipe
Prep time: 10 min
Cook time: 35 min
Total time: 45 min
Cuisine: American Southern
Ingredients: 3 large sweet onions (such as Vidalia), sliced into ½-inch rings; 1 ½ cups shredded cheddar cheese; 1 cup shredded Monterey Jack cheese; ½ cup grated Parmesan cheese; 4 tablespoons unsalted butter, melted; 1 teaspoon garlic powder; ½ teaspoon dried thyme; ½ teaspoon salt; ¼ teaspoon black pepper

Tennessee Onions: Cheesy Baked Sweet Onion Casserole Recipe is a comforting side dish that brings the sweet, mellow flavors of Vidalia onions together with a gooey, golden cheese crust. It's perfect for family dinners, potlucks, or anytime you want to elevate simple sweet onions into something special. I like making this casserole when the oven's already on for other dishes-it fills the kitchen with a toasty aroma that's hard to resist.

Tennessee Onions: Cheesy Baked Sweet Onion Casserole Recipe - Recipe Image — Tennessee Onions, Cheesy Baked Sweet Onion Casserole, Vidalia onion side dish, cheesy onion casserole recipe, baked sweet onion side dish

Jump to:

Why This Recipe Works
Ingredient Game Plan
How to Cook Tennessee Onions: Cheesy Baked Sweet Onion Casserole Recipe
Pro Moves I Swear By
Serve It Up
Make-Ahead & Storage
Frequently Asked Questions
Final Thoughts
Complete Recipe

🍳

Why This Recipe Works

This luscious casserole thrives on the natural sweetness of the onions combined with a blend of three cheeses that provide creaminess, tang, and a satisfyingly crispy top. It's straightforward, requiring minimal prep yet delivering maximum flavor that feels both homey and a bit indulgent.

Consistent Texture: Slicing onions into uniform rings ensures even roasting and cheese coverage, preventing mushy or dry spots.
Deep, Balanced Flavor: Garlic, thyme, and a pinch of pepper add subtle complexity without overpowering the sweet onions.
Simple Ingredients: Using a combination of cheddar, Monterey Jack, and Parmesan creates layers of flavor with a rich, melty, golden finish.
Fast Prep, Big Payoff: With just about 10 minutes of prep and straightforward layering, this recipe fits easily into busy weeknights or holiday spreads.

Ingredient Game Plan

Choosing the right ingredients makes all the difference in this Tennessee Onions: Cheesy Baked Sweet Onion Casserole Recipe. Fresh, sweet onions and good-quality cheese elevate the dish effortlessly.

Sweet onions (Vidalia): These are the star, so pick firm, large, and sweet onions to keep the casserole naturally sugary and tender when baked.
Cheddar cheese: Sharp cheddar adds boldness; go for freshly shredded to ensure smooth melting.
Monterey Jack cheese: This cheese melts beautifully and balances sharp cheddar with a creamy mildness.
Parmesan cheese: Freshly grated Parmesan brings a nutty, savory punch and helps the crust crisp up perfectly.
Unsalted butter: Use melted butter for even coating and rich flavor without added saltiness.
Seasonings: Garlic powder, dried thyme, salt, and pepper enhance the sweetness of the onions without stealing the spotlight.

Quick Note: Exact measurements and full instructions are listed at the bottom in the printable recipe card.

How to Cook Tennessee Onions: Cheesy Baked Sweet Onion Casserole Recipe

Step 1 - Prep & Season

Start by preheating your oven to 375°F (190°C). While it warms up, lightly grease a 9x13-inch baking dish to keep the casserole from sticking and to promote even baking. Then, slice your sweet onions into ½-inch thick rings. I find peeling and slicing them evenly is key - it helps them cook uniformly and look beautiful in layers. Spread the rings out in the dish, separating as much as you can so the butter and seasoning reach every nook. Drizzle the melted butter evenly over the onions, then sprinkle garlic powder, thyme, salt, and black pepper on top for that gentle flavor boost.

Step 2 - Build Flavor

Now it's time to layer on the cheeses. Distribute the shredded cheddar and Monterey Jack across the onions for creamy richness, then finish with grated Parmesan sprinkled on top. The Parmesan is what will give you that irresistible golden crust. When layering, I like to press the cheese down slightly with a spatula to ensure it sticks well to the onions. Cover the whole dish tightly with foil to trap moisture and let the onions soften gently without the cheese browning prematurely.

Step 3 - Finish for Best Texture

Bake the casserole covered for 25 minutes, checking the edges for tender, translucent onions that have released their sweetness. Then remove the foil and continue baking for an additional 10 minutes. This uncovered time is crucial-it lets the top cheese bubble, turn golden, and develop crispy edges that contrast beautifully with the soft onions underneath. If you see the cheese browning too quickly, tent loosely with foil again to prevent burning while the onions finish cooking. When it's done, let it rest for 5 minutes before serving so the cheese sets up slightly, making it easier to scoop.

📎

Pro Moves I Swear By

Having made this Tennessee Onions: Cheesy Baked Sweet Onion Casserole Recipe more times than I can count, I've learned a few tricks that keep it tasting fresh and delicious every time.

Doneness Cue: The onions should be soft and just starting to caramelize around the edges before removing the foil for that perfect tender bite.
Temperature Trick: Baking at 375°F balances melting the cheese and softening the onions without drying the dish.
Make-Ahead Move: You can prep the whole casserole the day before and keep it covered in the fridge; just add 5 extra minutes to baking time.
Skip This Pitfall: Don't slice your onions too thin or they'll turn mushy; aim for ½-inch thickness to maintain structure.

Serve It Up

Finishing Touches

A sprinkle of fresh chopped parsley or chives after baking adds a pop of color and freshness that complements the rich, cheesy casserole. I like serving it warm because the cheeses are silky and gooey, but it's also delicious at room temperature if you're taking it to a potluck. A little dollop of sour cream or a drizzle of hot sauce alongside can elevate it even further, giving you a bit of creamy tang or heat to balance the sweetness.

Great Pairings

This casserole pairs beautifully with roasted chicken, grilled pork chops, or a simple steak. For veg eaters, it's a fantastic partner to lentil loaf or crispy tofu. I often serve it with something crisp and green like a simple mixed salad or roasted Brussels sprouts to provide a refreshing contrast to the rich, cheesy sweetness.

Easy Plating Wins

Serve the Tennessee Onions: Cheesy Baked Sweet Onion Casserole Recipe right from the baking dish for a warm, homey vibe, or scoop it neatly onto plates, layering it on a bed of greens or alongside your main. For a special occasion, garnish each serving with a sprig of thyme or a little extra Parmesan for that elegant touch. No need to fuss; the golden cheese crust is beautiful on its own.

Make-Ahead & Storage

Storing Leftovers

Store leftovers in an airtight container in the refrigerator for up to 3-4 days. The texture of the onions softens a little more when chilled, and the cheese firms up, but it reheats beautifully. I recommend warming it gently to bring back a bit of that silky, gooey cheese feel. Avoid stacking heavy items on top to keep the crust intact.

Freezer Notes

This casserole freezes okay, though the texture of the onions shifts slightly. Cool completely, then wrap tightly with plastic wrap and aluminum foil or store in a freezer-safe container for up to 2 months. Thaw overnight in the fridge before reheating to preserve moisture and prevent the cheese from separating too much.

Reheating Tennessee Onions: Cheesy Baked Sweet Onion Casserole Recipe Without Drying Out

To reheat without drying, cover the casserole or portion with foil and warm in a 350°F oven for 15-20 minutes until bubbly. You can also microwave single portions covered with a damp paper towel to keep moisture in, heating in 30-second increments until hot. If you have an air fryer, try 320°F for 6-8 minutes-just check to avoid over-crisping. A splash of cream or a small pat of butter before reheating helps refresh that creamy texture.

Frequently Asked Questions

Can I use regular onions instead of sweet onions in this recipe?

You can, but sweet onions like Vidalias have a naturally mild and sugary profile that's perfect for this casserole. Regular onions might have a sharper bite and could alter the overall flavor balance.

Do I need to pre-cook the onions before baking?

No pre-cooking is needed. The baking process with the foil cover gently softens the onions while melting the cheese, keeping the texture delicate but firm.

Can I make this casserole vegan or dairy-free?

Absolutely! Swap the cheeses for vegan alternatives and use plant-based butter. The texture changes a bit but it still bakes up deliciously cheesy and sweet.

What's the best way to reheat leftovers without drying them out?

Reheat covered in a moderate oven or microwave with a loose cover to trap moisture. Adding a small splash of cream or butter before reheating works wonders to keep the sauce silky.

Final Thoughts

This Tennessee Onions: Cheesy Baked Sweet Onion Casserole Recipe is one of those dishes that feels like a warm hug on a plate. It's simple, dependable, and shines brightest when made with care. I hope you'll try it soon and discover how easy it is to transform humble onions into a rich, cheesy sensation your whole family will love. Cooking together, even in small ways like this, always brings me a little joy-I think it will for you, too.

Complete Recipe