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Green Bean Casserole

  • Author: Briana Thomas
  • Total Time: 1 hour 30 minutes
  • Yield: 12-15 servings


This low carb Green Bean Casserole will help you maintain your holiday traditions without sacrificing any flavor! The topping is reminiscent of French fried onions. Yum! THM S


  • 3 12-ounce bags frozen green beans (thawed)



  • 8 ounces fresh mushrooms
  • 1 cup light sour cream
  • 3/4 cup plain unsweetened almond milk
  • 1/4 cup oat fiber
  • 2 teaspoons salt
  • 1 teaspoon onion powder
  • 3/4 teaspoon black pepper



  • 1 large yellow onion (sliced)
  • 2 tablespoons salted butter



Blend the mushroom soup ingredients together until smooth – I used my Vitamix blender. Mix the soup with the green beans in a large mixing bowl and spread into a greased 9” x 13” glass baking pan. Cover with foil and bake at 350° for 40 minutes.

While the casserole is baking, make the topping. Sauté the sliced onion in the butter in a skillet until nicely browned (this takes a while). I like to start cooking the onions with a lid on the pan to expedite the cooking process, then remove it after the onions are soft to reduce any liquid and let the onions brown. When the onions are brown, take the pan off the heat and let the onions cool before adding the cheese and cracker crumbs.

When the casserole has finished its first 40 minutes of baking, remove it from the oven and take the foil off. Mix the shredded cheddar and cracker crumbs into the cooled onions, then spread the topping evenly over the casserole.

Bake uncovered for another 20 minutes or until the beans are tender and the topping is golden brown.

This green bean casserole is best fresh as most things are, but you can make it ahead and reheat if you need to. You could possibly do the first bake ahead of time, then add the topping and do the final bake to warm it through before serving. (If the casserole is cold from the fridge, you may need to bake more like 30-40 minutes to warm it through.) That may be better than baking it all the way, then baking it again to heat it.


Frozen vs canned green beans: I have not tried canned green beans in this recipe, but I imagine that they would work and you would not have to bake the casserole as long. I would drain the beans well, mix them with the mushroom soup, and spread them into the pan. Skip the first bake with the foil and just add the topping right away, then bake uncovered for 30-40 minutes until the casserole is heated through. If you try this, comment below and let me know how it goes!

Wasa or Ryvita crackers: If you need to be gluten free, omit these and try using some additional cheese instead. I often find these crackers at salvage/discount stores. Walmart or local grocery stores usually carry a variety or two as well.

Allergy info: egg free and nut free – use carton coconut milk instead of almond milk if needed (most people with tree nut allergies can have coconut products, but confirm with your doctor). For a gluten free option, use gluten free oat fiber and follow the note above to replace the Wasa crackers.

This is an update of the Green Bean Casserole recipe on page 124 of Necessary Food. This recipe is a double batch made in a larger pan so you can feed a crowd. I added mushrooms to the soup for a mushroom soup flavor, added an onion topping reminiscent of French fried onions, and bumped up the spice and flavor.

This recipe was originally published to the blog on December 22, 2015. It was updated November 2021.

  • Prep Time: 30 mins
  • Cook Time: 60 mins
  • Category: Side Dish
  • Method: Bake
  • Cuisine: THM S, low carb

Keywords: thm, trim healthy mama, thm green bean casserole, low carb green bean casserole, gluten free green bean casserole, healthy green bean casserole, thm thanksgiving recipes