If you’re on the hunt for a side dish that turns ordinary onions into a show-stopping centerpiece, look no further than Tennessee Onions. Imagine tender, sweet onion slices mingling with a trio of gooey, golden cheeses—all sprinkled with aromatic herbs and baked to bubbly perfection. This classic southern casserole brings humble ingredients together in a way that’s utterly irresistible, and it’s just as at home on a holiday table as it is beside a weeknight roast. Savory, cheesy, and nearly effortless, Tennessee Onions are the ultimate comfort food to share with family and friends.

Ingredients You’ll Need

What I love most about Tennessee Onions is how a handful of pantry staples comes together for such huge flavor. Each element pulls its weight here, contributing a unique note—whether it’s sweetness, rich umami, or that famously melty cheese pull everyone will reach for!

Sweet onions: Vidalia or another mild variety works best for those signature tender, sweet slices that soak up all the flavors as they bake.
Unsalted butter: Adds richness and helps the onions caramelize and soften in the oven.
Garlic powder: Gives a savory depth and subtle punch that balances the sweetness of the onions.
Salt: Enhances all the flavors and keeps the dish from tasting flat—don’t skip it!
Black pepper: Offers just a hint of earthy spice that complements the dairy and onion sweetness.
Dried thyme (optional): Lends a woodsy, herbaceous note that makes the whole dish smell incredible.
Shredded mozzarella cheese: Known for melting beautifully and stretching into molten ribbons over the onions.
Shredded cheddar cheese: Delivers sharp, creamy flavor and that classic golden color on top.
Grated Parmesan cheese: Rounds everything out with nutty, salty complexity and a crave-worthy crispy finish.
Fresh parsley (optional): A bright and vibrant garnish for added freshness and a pop of color.

How to Make Tennessee Onions

Step 1: Prep Your Pan and Onions

Start by preheating your oven to 375°F (190°C) and lightly greasing a 9×13-inch baking dish. Thinly slice your sweet onions—aim for slices about 1/4-inch thick so they soften nicely but still hold a bit of bite. Evenly spread the sliced onions right into your prepared dish, allowing some overlap to ensure every forkful scoops up plenty of flavor.

Step 2: Butter, Season, and Toss

Dot the surface of your onions with bits of unsalted butter. Next, sprinkle over the garlic powder, salt, black pepper, and dried thyme if you’re using it. Gently toss or stir the onions in the pan to make sure every layer is coated with butter and seasoning—this step promises big taste in every bite.

Step 3: Layer on the Cheese

Now comes the magic! Sprinkle the shredded mozzarella, cheddar, and Parmesan cheeses evenly across the onion mixture. Don’t be afraid to pile it on—generous cheese coverage is what gives Tennessee Onions their ultra-comforting, decadent appeal.

Step 4: Cover, Bake, and Finish

Cover your baking dish with foil and place it in the oven for 25 minutes. This helps the onions steam and get wonderfully soft. Once time’s up, remove the foil and return the dish to the oven for another 15 to 20 minutes, or until the cheese is bubbling and golden brown and the onions are completely tender. If you like extra color on top, give the dish a quick broil at the very end.

How to Serve Tennessee Onions

Garnishes

A final shower of fresh chopped parsley adds both freshness and color contrast, making the gooey, cheesy onions look even more inviting. You could also try a sprinkle of green onions or a pinch of extra Parmesan for a little sparkle.

Side Dishes

Tennessee Onions are a cozy, versatile side that pairs with just about anything! They shine alongside grilled steak, roast chicken, barbecue, or a juicy pork chop. For a southern feast, serve them next to cornbread, mashed potatoes, or collard greens and watch everyone come back for seconds.

Creative Ways to Present

Try baking Tennessee Onions in individual ramekins for a dinner party-worthy presentation—everyone loves having their own bubbly bowl. You can also use leftovers as a cheesy topping for baked potatoes, burgers, or even spread over toast for a truly indulgent snack.

Make Ahead and Storage

Storing Leftovers

Allow the onions to cool completely before covering the dish tightly with foil or transferring to an airtight container. Stored in the refrigerator, Tennessee Onions will stay fresh and tasty for up to 3 days—if they last that long!

Freezing

While the texture of the onions may change a bit, you can freeze Tennessee Onions after baking. Place portions in freezer-safe containers, label, and freeze for up to a month. Thaw in the refrigerator overnight before reheating.

Reheating

To revive that melty, cheesy magic, reheat leftovers in a 350°F oven, covered, until hot throughout (about 15–20 minutes). For smaller servings, the microwave also works—just watch so the cheese doesn’t overcook. A quick sprinkle of fresh parsley after reheating really brightens things up.

FAQs

Can I use yellow or red onions instead of sweet onions?

Yes, you can substitute with yellow or even red onions if you’d like, but sweet onions like Vidalia are traditional for Tennessee Onions and provide the mellow flavor that makes this dish so lovable.

Is it necessary to caramelize the onions before baking?

Caramelizing the onions isn’t required, but if you have a few extra minutes, giving them a quick sauté until lightly golden will take the flavor up a notch and add even more richness.

Can I prepare Tennessee Onions ahead of time?

Absolutely! Assemble the dish up through the cheese layer, then cover and refrigerate up to 24 hours before baking. You may need to add a few extra baking minutes if starting from cold.

What’s the best way to slice the onions?

A sharp knife or mandoline ensures even, thin slices—about 1/4-inch thick—so they cook evenly and become perfectly soft while still holding their shape beneath all that cheese.

Can I make Tennessee Onions without one of the cheeses?

You can definitely adjust the cheese blend to your taste, as long as you use enough to cover the onions generously. Feel free to use all cheddar, or swap for your own favorite melting cheeses.

Final Thoughts

If you crave a side that wows with every forkful, you simply have to try Tennessee Onions. This recipe transforms everyday ingredients into something greater than the sum of its parts, and I promise, the cheesy, savory payoff is worth every minute. Whether you make it for a special occasion or a simple weeknight, Tennessee Onions will have everyone scooping up seconds—so enjoy and make it your own!

Tennessee Onions Recipe

5 Stars 4 Stars 3 Stars 2 Stars 1 Star

4.7 from 7 reviews

Author: Emma
Total Time: 50 minutes
Yield: 6 servings 1x
Diet: Vegetarian

Print Recipe

Description

Tennessee Onions is a mouthwatering baked onion dish loaded with three types of cheese and savory seasonings, creating a comforting and flavorful side that pairs perfectly with grilled meats or serves as a standalone vegetarian delight.

Ingredients

Scale

Main Ingredients:

3 large sweet onions (like Vidalia), thinly sliced
2 tablespoons unsalted butter

Seasonings:

1 teaspoon garlic powder
1/2 teaspoon salt
1/2 teaspoon black pepper
1/2 teaspoon dried thyme (optional)

Cheeses:

1 cup shredded mozzarella cheese
1 cup shredded cheddar cheese
1/2 cup grated Parmesan cheese

Garnish:

Fresh parsley for garnish (optional)

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Instructions

Preheat Oven: Preheat the oven to 375°F (190°C) and lightly grease a 9×13-inch baking dish.
Prepare Onions: Spread the sliced onions in the dish. Dot with butter, sprinkle with garlic powder, salt, pepper, and thyme if using. Toss to coat.
Add Cheeses: Sprinkle mozzarella, cheddar, and Parmesan cheeses over the top.
Bake: Cover with foil and bake for 25 minutes. Uncover and bake for 15–20 minutes until onions are tender and cheese is golden and bubbly.
Garnish: Garnish with fresh parsley if desired.