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The Best Homemade Healthy Green Bean Casserole

The BEST homemade healthy green bean casserole made with fresh green beans, mushrooms and topped with homemade crunchy onions. Lightened up from traditional versions and perfect for the holidays!
Course Nut Free, Side Dish, Thanksgiving, Vegetarian
Cuisine American
Keyword green bean casserole, healthy green bean casserole
Prep Time 30 minutes
Cook Time 1 hour
Total Time 1 hour 30 minutes
Servings 10 servings
Calories 159 kcal
Author Monique Volz of AmbitiousKitchen.com


  • For the onions:
  • 2 medium to large yellow onions, thinly sliced
  • 1 tablespoon olive oil
  • 1/2 cup all-purpose flour (or whole wheat pastry flour or gluten free oat flour)
  • 1/2 cup panko breadcrumbs
  • 1/2 teaspoon garlic powder
  • 1/2 teaspoon salt
  • For the green beans:
  • 2 pounds fresh green beans, trimmed
  • For the mushrooms:
  • 2 tablespoons butter, divided
  • 1 pound (16 ounces) sliced baby bella mushrooms
  • 1 teaspoon fresh thyme
  • Salt and pepper
  • For the sauce:
  • 2 tablespoons butter
  • 1/3 cup all purpose flour (or whole wheat pastry flour or all purpose GF flour)
  • 2 cups low sodium chicken broth (or vegetarian broth)
  • 3 cloves garlic, minced
  • 1/2 cup grated parmesan cheese
  • Freshly ground salt and pepper, to taste


  1. Preheat oven to 425 degrees F. Line a large baking sheet with parchment paper and spray with nonstick cooking spray. Set aside.

  2. Place sliced onions in a large bowl, drizzle with 1 tablespoon of olive oil then add in flour, panko bread crumbs, garlic powder and salt. Use your hands to toss to combine, then place onions onto prepared baking sheet and bake for 15-25 minutes, using a tong to toss the onions every 8-10 minutes or so, until nice and crispy.

  3. Once done cooking, set onions aside. Reduce the heat in the oven to 350 degrees F.
  4. While the onions are cooking, bring a large pot of salted water to a boil. Add green beans in two batches, cooking for about 2-3 minutes per batch. I like to remove the green beans from the water with metal tongs and transfer to a large bowl, then repeat with additional green beans. Set aside.
  5. Next cook your mushrooms: Place a large skillet over medium-high heat and add in 2 tablespoons butter. Once butter melts, add in the mushrooms, fresh thyme and salt and pepper. Cook mushrooms, stirring occasionally until mushrooms are nice and golden brown; about 4-6 minutes. Transfer to a bowl.
  6. In the same skillet you cooked the mushrooms, add in 2 tablespoons of butter and place over medium heat. Once butter melts, whisk in flour and cook for 15-30 seconds until a paste forms, then VERY slowly add 2 cups of the broth, while you continue to whisk away any lumps. You’ll need to whisk pretty vigorously. 

  7. Once smooth, increase heat, and bring mixture to a boil, then reduce heat and simmer for 5 minutes stirring every so often until sauce thickens up a bit, similar to a gravy. If it gets way too thick, add in 1/4-½ cup more broth. 

  8. Once thick, turn off the heat and stir in minced garlic and parmesan cheese. Season with salt and pepper to taste.

  9. Spray a 2 quart baking disk or 9x13 inch baking pan with nonstick cooking spray, or grease with olive oil or butter. Add in green beans, mushrooms and 1/4 of the crispy onions; gently toss together. 
  10. Pour the sauce all over, then cover with foil and bake for 25-30 minutes. Remove foil, add the remaining crispy onions on top and bake for 5-10 more minutes. Serves 8-10

Recipe Notes

To make gluten free: use gluten free breadcrumbs and gluten free all purpose flour.

To make ahead of time:

  1. Prepare the recipe as directed, including adding the remaining 3/4 of the crispy onions on top. Do not bake. Wrap with foil and place in fridge up to 2 days ahead.
  2. Once ready, bake as directed. Removing foil during the last 10-20 minutes of baking to crisp up the onions a bit.
  3. Serve immediately with all your favorite Thanksgiving dishes.
Nutrition Facts
The Best Homemade Healthy Green Bean Casserole
Amount Per Serving (1 serving)
Calories 159 Calories from Fat 60
% Daily Value*
Fat 6.7g10%
Saturated Fat 3.4g21%
Carbohydrates 18.2g6%
Fiber 3.44g14%
Sugar 4.8g5%
Protein 7.2g14%
* Percent Daily Values are based on a 2000 calorie diet.