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    Home » Recipes » Side Dishes

    Scalloped Onions

    Published: Apr 21, 2025 · by Jan Nunes

    Scalloped onions in a white baking dish and garnished with fresh thyme with text overlays.
    Scalloped onions in a white baking dish and garnished with fresh thyme with text overlays.

    Scalloped Onions are a delicious side dish of sliced onions smothered in a rich and creamy Béchamel sauce and then baked to perfection.

    Tired of the same old roasted potatoes or steamed vegetables? Often overlooked or used only as an aromatic in cooking, onions can be the star of a creamy casserole.

    Sweet but savory, these Scalloped Onions will melt in your mouth and are a great accompaniment to any roasted meat.

    Scalloped onions in a white baking dish and garnished with fresh thyme.
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    Jump to:
    • About This Recipe
    • Ingredient Notes
    • How to Make Scalloped Onions
    • My Top Tip
    • Make-Ahead, Storage, & Reheating Instructions
    • More Side Dishes You'll Love
    • 📖 Recipe
    • 💬 Comments

    About This Recipe

    This recipe was inspired by combining the ideas behind the casserole "Tennessee Onions, "Creamed Pearl Onions" (which are spectacular for steak dinners and holidays), and "Scalloped Potatoes."

    The recipe is essentially an easy-to-make Béchamel sauce loaded with sliced, sweet yellow onions that are par-baked. Par-baking accomplishes two tasks:

    1. The sliced onions are more easily separated into rings.
    2. The onion's flavor becomes sweeter and less sharp.

    I love the beautiful way this casserole looks. Although you could simply slice the onions and mix them into the sauce, and then bake them, I love stacking the onion rings so that they look like roses nestled in the sauce.

    To finish off the casserole, I generally reserve a pinch each of the freshly ground black pepper and nutmeg and sprinkle them over the onions before baking. Lastly, a generous dusting of thyme leaves makes a gorgeous garnish before serving. Doesn't this sound delicious and beautiful? Great!

    So, let's cook!

    Ingredient Notes

    Scalloped Onions Ingredients, clockwise from top left: salted butter, Wondra flour, sliced onions, whole milk, heavy cream, fresh thyme, ground nutmeg, black pepper, grated Romano cheese, and salt.

    Here's what you need:

    • Yellow Onions - I prefer to use yellow onions, but you can use red, too. Do not use white onions as they have a sharp flavor.
    • Salted Butter - Salted butter is best, but you can use unsalted butter and add an extra ¼ teaspoon of salt when making the Béchamel sauce.
    • Wondra Flour - Wondra is a flour specifically milled for use in making sauces and gravies. If you do not have Wondra you can use all-purpose flour.
    • Whole Milk - Whole milk has the best flavor for making creamed dishes.
    • Heavy Cream - Heavy cream makes a deliciously rich Béchamel sauce.
    • Salt - Just plain salt from the round blue box works great.
    • Black Pepper - I always use freshly ground black pepper. It's aroma and flavor are pleasantly sharp and flowery.
    • Ground Nutmeg - You can use pre-ground nutmeg, but fresh will be more fragrant with lemon overtones.
    • Grated Romano Cheese - Romano cheese makes the sauce savory and delicately cheesy, letting the onions be the star of the dish.
    • Fresh Thyme Leaves - Fresh thyme is wonderful with onions. However, you can use a small amount of dried if fresh is not available.
    • Butter-Flavored Non-Stick Cooking Spray - I love using a butter-flavored cooking spray to grease the dish, and I also use a light spray on the onions before they are parbaked.

    Please see the recipe card for the exact quantities.

    How to Make Scalloped Onions

    Process Photo 1a - Sliced onions on a parchment-lined baking sheet seasoned with salt and pepper.

    Prepare the Onions. Preheat an oven to 350°F/177°C.

    Peel the onions and slice them, crosswise, 1” thick. Place the sliced onions on a parchment-covered baking sheet and spray with butter-flavored cooking spray. Lightly season with salt and pepper, if desired.

    Process Photo 1b - The baked & softened onions are separated into rings on the baking sheet.

    Par-bake for 15 minutes to slightly soften the onions and remove bitterness. Remove from oven and let cool while making the Béchamel sauce. Separate the cooled slices into groups of rings that look like roses.

    Process Photo 2a through 2d - Making Béchamel sauce 2a- Cooking the roux. 2b - Adding milk and cream to the roux. 2c - Adding seasonings and Romano cheese to the cooked sauce. 2d - The finished Béchamel sauce.

    Make Béchamel Sauce. In a heavy-bottomed medium-sized saucepan, melt the butter over medium-low heat. Add the flour. Stir and cook the butter and flour for 3 to 4 minutes until the flour is fully incorporated into the butter and well-cooked but not brown.

    Whisk in the milk and heavy cream, and stir well to avoid lumps. Cook over medium heat until the sauce comes to a simmer and has thickened.

    Immediately add salt, freshly ground black pepper, nutmeg, and Romano cheese. Taste and adjust seasoning if needed.

    Process Photo 3 - Rings of onion are stacked to resemble roses and nestled in the Béchamel sauce in the baking dish.

    Assemble the Casserole. Grease the bottom and sides of a 10” x 8” casserole or baking dish with butter-flavored cooking spray. Pour the Béchamel sauce into the prepared dish. Arrange the par-baked sliced onions in the pan to make rosettes by placing smaller rings inside larger ones.

    Bake. Bake the uncovered casserole for 25 minutes or until hot and bubbly. Then broil on high for 3 to 5 minutes or until the onions are slightly browned.

    Scalloped onions in a white baking dish and garnished with fresh thyme.

    Garnish with fresh thyme leaves or chopped parsley. Serve and Enjoy!

    My Top Tip

    ♡ Don't skip par-baking the onions. Not only are the onions easier to separate into rings, but they also become less sharp in flavor.

    Make-Ahead, Storage, & Reheating Instructions

    • Make-Ahead: Assemble this casserole up to baking it and cover it with aluminum foil. Bring the scalloped onion casserole to room temperature before baking it. It may need to bake longer.
    • Refrigeration: Store leftovers in a sealed container for up to 3 days.
    • Freezing: Do not freeze. Because this casserole contains dairy it will not freeze well.
    • Reheating: Reheat gently in the microwave or the oven.
    Scalloped onions in a white baking dish and garnished with fresh thyme.

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    ♡ Did you love this recipe for Scalloped Onions? Please leave a 🌟 star rating and let me know how things went in the ✍ comments below. Thanks for visiting!

    📖 Recipe

    Scalloped onions are in a white baking dish and garnished with fresh thyme.

    Scalloped Onions

    5 from 1 vote
    By: Jan Nunes
    Scalloped Onions are a delicious side dish of sliced onions smothered in a rich and creamy Béchamel sauce and then baked to perfection.
    Print Share Pin Email
    Prep Time ~ 20 minutes minutes
    Cook Time ~ 35 minutes minutes
    Broiling Time ~ 5 minutes minutes
    Total Time ~ 1 hour hour
    Servings ~ 8 Servings
    Calories ~ 297kcal
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    Ingredients
     

    • Butter-Flavored Non-Stick Cooking Spray
    • 3 Pounds Yellow Onions, Peeled and Sliced 1” Thick
    • 4 Tablespoons Salted Butter
    • 4 Tablespoons Wondra Flour or All-Purpose Flour
    • 2 Cups Whole Milk
    • 1 Cup Heavy Cream
    • ½ Teaspoon Salt
    • ½ Teaspoon Black Pepper, Freshly Ground
    • ½ Teaspoon Ground Nutmeg
    • ⅓ Cup Grated Romano Cheese
    • 1 Tablespoon Fresh Thyme Leaves, or Chopped Parsley

    Instructions
     

    • Prepare the Onions. Preheat an oven to 350°F/177°C.
      Peel the onions and slice them, crosswise, 1” thick. Place the sliced onions on a parchment-covered baking sheet and spray with butter-flavored cooking spray. Lightly season with salt and pepper, if desired.
      Par-bake for 15 minutes to slightly soften the onions and remove bitterness. Remove from oven and let cool while making the Béchamel sauce. Separate the cooled slices into groups of rings that look like roses.
      3 Pounds Yellow Onions, Butter-Flavored Non-Stick Cooking Spray
    • Make Béchamel Sauce. In a heavy-bottomed medium-sized saucepan, melt the butter over medium-low heat. Add the flour. Stir and cook the butter and flour for 3 to 4 minutes until the flour is fully incorporated into the butter and well-cooked but not brown.
      Whisk in the milk and heavy cream, and stir well to avoid lumps. Cook over medium heat until the sauce comes to a simmer and has thickened.
      Immediately add salt, freshly ground black pepper, nutmeg, and Romano cheese. Taste and adjust seasoning if needed.
      4 Tablespoons Salted Butter, 4 Tablespoons Wondra Flour or All-Purpose Flour, 2 Cups Whole Milk, 1 Cup Heavy Cream, ½ Teaspoon Salt, ½ Teaspoon Black Pepper, ½ Teaspoon Ground Nutmeg, ⅓ Cup Grated Romano Cheese
    • Assemble the Casserole. Grease the bottom and sides of a 10” x 8” casserole or baking dish with butter-flavored cooking spray. Pour the Béchamel sauce into the prepared dish. Arrange the par-baked sliced onions in the pan to make rosettes by placing smaller rings inside larger ones.
    • Bake. Bake the uncovered casserole for 25 minutes or until hot and bubbly. Then broil on high for 3 to 5 minutes or until the onions are slightly browned.
      Garnish with fresh thyme leaves or chopped parsley. Serve and Enjoy!
      1 Tablespoon Fresh Thyme Leaves

    Nutrition

    Calories: 297kcal | Carbohydrates: 24g | Protein: 7g | Fat: 20g | Saturated Fat: 13g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 5g | Trans Fat: 0.2g | Cholesterol: 61mg | Sodium: 338mg | Potassium: 392mg | Fiber: 3g | Sugar: 11g | Vitamin A: 811IU | Vitamin C: 14mg | Calcium: 195mg | Iron: 1mg

    Per 1 serving. All nutritional information on this site is an estimate. Your results may vary.

    Encharted Cook™ or Jan Nunes shall not be liable for adverse reactions or any other outcome resulting from the use of recipes or recommendations on this website or actions you take as a result.

    © 2018-2025 Encharted Cook, Jan Nunes. All rights reserved.

    Course: Side Dish
    Cuisine: American, French

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    Comments

      5 from 1 vote

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      Recipe Rating




    1. Jan Nunes says

      April 22, 2025 at 3:32 pm

      5 stars
      We love serving these creamy beautiful onions with Baked Potatoes and a Standing Rib Roast. They are amazing with the meat or on top of a baked potato.

      Reply
    Jan Nunes

    Hey There!

    Welcome to Encharted Cook! I'm Jan, a seasoned cook with recipe charts, pro tips, and ideas to help you make delicious dinners. Over the years I've learned that many recipes are related... and if you learn to make one delicious dish, you can make many more!

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