This Sweet Onion Casserole is a delicious twist on the classic side dish. This old-fashioned recipe takes sweet onions, layers them with tasty herbs and spices, tops them with a mix of flavorful cheeses, and finishes with a golden, buttery topping.
It's a perfect addition to any meal, whether it's a regular family dinner or a special occasion.
🗝️ Recipe's key points
- The blend of sweet onions, herbs, spices, and two types of cheese creates a delicious flavor. The mild Cheddar and smoked Gouda add a creamy and satisfying cheesy taste.
- Coarse bread crumbs from rustic bread or baguette provide a nice crunch against the soft onions and melted cheeses.
- The recipe is easy, with only 10 minutes of active time and a total of 1 hour and 20 minutes.
- This casserole complements various main dishes and is a standout side for any meal.
This onion casserole is delicious and easy to make, combining cheesy, buttery goodness with a satisfying crunch. It's a crowd-pleasing comfort dish with a nostalgic charm, suitable for any occasion.
This is an overview of the ingredients. You'll find the full measurements and instructions in the recipe card (printable) at the bottom of the page.
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- Sweet onions - such as yellow onions or Vidalia onions
- Dried thyme - you can also use fresh if you prefer
- Dried parsley flakes - fresh parsley can be used as well
- Garlic salt
- Dried oregano - or fresh, if you prefer
- Dry mustard
- Cayenne pepper - omit or adjust the quantities to suit your tastes
- Salted butter - cut into small pieces
- Mild Cheddar cheese - shredded
- Smoked Gouda cheese - shredded
- Smoked paprika
- Coarse bread crumbs - from rustic bread or baguette
- Melted butter
This is an overview of the instructions. Full instructions are in the recipe card at the bottom of the page.
- Preheat oven to 350°F and coat a 13x9-inch baking dish with cooking spray.
- Add sliced sweet onions, thyme, parsley, garlic salt, oregano, mustard, and cayenne pepper to a large mixing bowl.
- Toss to combine.
- Arrange onion mixture evenly in the baking dish.
- Place butter pieces over the onions and sprinkle with Cheddar and Gouda.
- Cover with foil and bake for 40 minutes until onions are soft and sides are bubbly.
- Meanwhile, in a small bowl mix melted butter with bread crumbs and set aside.
- Remove foil, sprinkle with smoked paprika, and top with buttered bread crumbs.
- Return to the oven.
- Bake uncovered at 350°F for an additional 30 minutes until the top is golden.
Store any leftover sweet onion casserole in an airtight container in the refrigerator. It's best to consume within 3-4 days for optimal freshness. To reheat, use a microwave for individual servings or a preheated oven at 350°F until warmed through.
- Experiment with different cheeses such as gruyère, fontina, or mozzarella for unique flavor variations.
- Try fresh herbs like chopped chives, rosemary, or basil instead of dried herbs for a fresher, herbaceous taste.
- Adjust the level of cayenne pepper to control the spiciness, or add a pinch of red pepper flakes for an extra kick.
- Use seasoned or herbed bread crumbs for added flavor in the crunchy topping.
- Combine different types of onions, such as red and yellow, for a colorful and diverse onion profile.
- Add crispy bacon bits between the layers for a smoky and savory element.
- I recommend always grating your own cheese since pre-grated cheese has anti-caking agents that make it not melt as well.
- If making your own bread crumbs, let them dry a bit before mixing with butter for a crunchier texture.
- Keep an eye on the casserole while baking to prevent burning. Adjust time if needed for the perfect golden finish.
No, you don't need to cook the onions beforehand. They soften and develop flavor during baking.
No, they're different. Vidalia onions are a type of sweet onion known for their mild flavor and are usually sweeter than regular yellow onions.
Vidalia onions are generally sweeter than yellow onions.
White onions are milder, yellow onions are versatile with a balanced flavor, and red onions are often sharper and add vibrant color to dishes.
The most flavorful onion is subjective, but red onions are often considered more pungent and bold in taste.
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🍽 What to serve with Sweet Onion Casserole
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Prepare to fall in love with this sweet onion casserole that seamlessly combines the caramelized goodness of sweet onions with a perfect blend of herbs, two types of melted cheese, and a satisfyingly crunchy topping.
Its rich, buttery flavor and versatile pairing options make it a surefire crowd-pleaser!
Tutti a tavolo, è pronto!
If you love this recipe please give it 5 stars ⭐️⭐️⭐️⭐️⭐️.
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Old-Fashioned Tennessee Sweet Onion Casserole
- 2 ½ lb. sweet onions about 3 large onions, sliced crosswise into ¼-in.-thick slices and separated into rings
- 1 tsp. dried thyme
- 1 tsp. dried parsley flakes
- 1 tsp. garlic salt
- ½ tsp. dried oregano
- ½ tsp. dry mustard
- ¼ tsp. cayenne pepper
- ¼ cup salted butter cut into ¼-in.-thick pieces
- 4 oz. mild Cheddar cheese shredded (about 1 cup)
- 4 oz. smoked Gouda cheese shredded (about 1 cup)
- ¼ tsp. smoked paprika
- ½ cup bread crumbs coarsely grated from a rustic bread loaf or baguette.
- 2 tablespoon melted unsalted butter
- Warm the oven: Preheat oven to 350°F. Coat a 13- x 9-inch baking dish with cooking spray. Gather your ingredients.
- Season the onions: Place onions in a large bowl. Sprinkle with thyme, parsley, garlic salt, oregano, mustard, and cayenne pepper; toss gently to coat. Arrange evenly in the prepared baking dish.
- Add toppings and bake: Arrange butter evenly over onions and sprinkle with Cheddar and Gouda. Cover with aluminum foil, and bake in a preheated oven until onions are soft and sides are bubbly about 40 minutes.
- Mix the 2 Tablespoons melted butter with the fresh bread crumbs. Set aside.
- Finish baking: Remove foil. Sprinkle with the smoked paprika and the buttered bread crumbs.
- Bake at 350°F until top is golden, about 30 minutes.