Amish Oatmeal Rhubarb Bars (with crumb topping)

These Oatmeal Rhubarb were surprisingly easy to make and tasted absolutely delicious with the soft oatmeal base filled with a sweet and tangy rhubarb filling! This recipe for Oatmeal Rhubarb bars was adapted to fit an 8 by 8 inch pan, to make enough for a 13 by 9 inch pan simply hit the 2x button in the recipe card. These oatmeal rhubarb bars were inspired by an old order Amish cookbook, hence the name- Amish Oatmeal Rhubarb Bars. If you enjoy Amish baked goods, you may also enjoy Amish chocolate whoopie pies, Amish chocolate cake with peanut butter frosting, Amish chocolate chip cookies, or Amish coconut cream pie.

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Oatmeal Rhubarb bars with crumb topping

Amish Oatmeal Rhubarb Bars (with crumb topping)

These easy rhubarb bars only require an oatmeal crumb base and a sweet and tangy cooked rhubarb filling, making a soft rhubarb bar that is nicely textured and has the perfect balance of sweet and tangy!
4.69 from 41 votes
Prep Time 20 minutes
Cook Time 30 minutes
Course Dessert
Cuisine Amish
Servings 9


  • 8 by 8 inch baking dish (linked below)
  • Mixing bowl (linked below)
  • sauce pan (linked below)
  • measuring cups (linked below)


  • 1 cup old fashioned rolled oats
  • 3/4 cup all purpose flour
  • 1/2 cup butter softened
  • 1/8 teaspoon salt
  • 1/8 teaspoon baking soda
  • 1/2 cup brown sugar packed

For the Rhubarb filling:

  • 1 1/2 cups chopped rhubarb
  • 3/4 cup granulated sugar
  • 1 tablespoon cornstarch heaping
  • 2 tablespoons water
  • 1/2 teaspoon vanilla extract


Preheat oven to 350 degrees.

  • Combine the ingredients for the crumb topping in a medium sized mixing bowl, mixing until only coarse crumbs remain.
  • Combine the chopped rhubarb, sugar, cornstarch and water in a 2 quart saucepan. Bring to a simmer over medium-high heat stirring frequently. Allow to cook for 5-10 minutes until the mixture is clear and the rhubarb has softened (keep stirring occasionally while cooking). Remove from heat and stir in vanilla extract, then allow to cool for 10 minutes, until no longer hot and the mixture has thickened a little more.
  • Press all but 2/3 cup of the oatmeal crumbs into the bottom of a greased or parchment lined 8 by 8 inch baking dish, ensuring no cracks remain. Pour the warm rhubarb filling over the oatmeal crumb base, then sprinkle the remaining crumbs over top.
  • Bake the rhubarb bars in the preheated oven for 30-40 minutes until golden on the bottom and the filling and crumb topping has set. Cool completely before cutting, then enjoy!


If you prefer, you can also blend the rhubarb filling after it has cooled a little. This will result in a smoother filling, but is optional. 
More notes and step by step photos below. 
Keyword Amish, Rhubarb bars, Oatmeal, Crumb Topping, Easy
Tried this recipe?Let us know how it was!

Equipment needed for these Amish Oatmeal Rhubarb Bars:

  • 8 by 8 inch baking dish I prefer to use a glass baking dish for baking these rhubarb bars in. Using glass makes it more convenient for checking the sides and bottom of the bars for doneness.
  • Mixing bowl Stainless steel mixing bowls are my favorite because of their durability and sturdiness.
  • Saucepan You will need a 2 quart saucepan to cook the rhubarb filling in.
  • Measuring cups I also prefer to use stainless steel measuring cups, an added bonus for me is that mine are dish washer friendly.

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Ingredients needed for these oatmeal rhubarb bars: Butter, water, brown sugar, baking soda, vanilla, cornstarch, rhubarb, sugar, rolled oats, flour and salt (not shown).

Step 1: Combine the ingredients for the oatmeal crumb base and crumb topping, until only coarse crumbs remain.


Be sure to use softened butter for the oatmeal crumb base to create a better crumb and also for easier mixing. If your butter is not yet soft enough to use, you can pop it in the microwave for around 10 seconds or more. Check the butter frequently while heating it, because you do not want it to melt.

Step 2: Combine all but the vanilla extract for the rhubarb filling in a medium sized saucepan. Stir frequently and cook over medium-high heat until the mixture is clear and the rhubarb has softened. Whisk in the vanilla extract and allow to cool for 10 minutes.


You will need to use a heaping tablespoon of cornstarch for the rhubarb filling. If the rhubarb filling is still too runny after it has cooled, you can return it to the heat and then add an additional 1/2-1 tablespoon of cornstarch mixed into water (be sure to mix with water before adding, to prevent lumps in the rhubarb filling). Allow to cook until clear, then remove from heat and cool again. If needed, additional vanilla can also be added after cooking, as cooking the vanilla can reduce the flavor.

Step 3: Press all but 2/3 cup of the oatmeal crumb into the bottom of an 8 by 8 inch pan, ensuring there are no cracks remaining.


If doubling this recipe you will need to reserve around 1 heaping cup of the crumb topping.

I prefer to use parchment paper when baking bars like these oatmeal rhubarb bars, simply because it makes lifting the bars to cut them much easier!

Step 3 continued: Pour the slightly cooled rhubarb filling over the crumb topping. Spreading evenly over the oatmeal base with a spatula if needed.

Step 3 continued: Sprinkle the reserved 2/3 cup of oatmeal crumbs evenly over the top of the rhubarb filling.

Step 4: Bake the oatmeal rhubarb bars in the preheated oven for 30-40 minutes, or until golden on the edges and bottom, and the filling has set. Allow to cool before cutting.


Because the rhubarb is cooked, the bars can be stored in an airtight container at room temperature for up to 5 days. The bars can also be wrapped and frozen for several months.

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4 thoughts on “Amish Oatmeal Rhubarb Bars (with crumb topping)”

  1. Looks fantastic! Now to find rhubarb in the region i live in… Probably won’t happen but I’ll dream of tasting these! 🙂

  2. Anita Biedermann

    5 stars
    I was looking for a simple recipe to use up some rhubarb and decided to try yours. I love it! I did cut back on the granulated sugar a little, as I like my rhubarb desserts on the tart side. The oatmeal crumb crust and topping were perfect. I will be making this again! Thank you!

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