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Amish Oatmeal Rhubarb Bars

Amish oatmeal rhubarb bars feature thick rhubarb filling sandwiched between buttery oat crust layers. Bake until golden brown, then cool fully so the filling sets cleanly for bar slices.
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Prep Time 20 minutes
Cook Time 40 minutes
Cooling 1 hour
Total Time 2 hours
Servings: 16 servings
Course: Dessert
Cuisine: American
Calories: 310
Ingredients Equipment Method Notes

Ingredients
  

For crust and topping
  • 2 cup all-purpose flour
  • 2 cup old-fashioned oats
  • 1.5 cup brown sugar
  • 1 tsp baking soda
  • 0.5 tsp salt
  • 1 lb butter Use melted butter.
For filling
  • 4 cup fresh rhubarb, diced
  • 1.5 cup sugar
  • 0.25 cup cornstarch
  • 1 cup water
  • 1 tsp vanilla extract

Equipment

  • 1 sheet pan

Method
 

Prep and build the crust
  1. Preheat oven to 350°F and grease a 9x13-inch baking pan so the bars release cleanly.
  2. In a bowl, combine all-purpose flour, old-fashioned oats, brown sugar, baking soda, and salt, then stir until evenly mixed.
  3. Pour in melted butter and mix until the mixture becomes crumbly.
  4. Press half of the oat mixture into the bottom of the prepared pan to form an even base layer.
Cook the rhubarb filling
  1. In a saucepan, combine rhubarb, sugar, cornstarch, water, and vanilla extract.
  2. Cook over medium heat for about 10 minutes, stirring, until thickened and glossy (visual cue: it should mound slightly on the spoon).
  3. Spread the rhubarb filling over the pressed crust in an even layer.
  4. Sprinkle the remaining oat mixture on top to create the crumble layer.
Bake and cool
  1. Bake at 350°F for 35-40 minutes until golden brown, with crisp-looking edges (visual cue: the top should feel set when tapped).
  2. Cool completely before cutting into bars so the filling firms up and slices hold together.

Notes

Pro tip: cool the bars all the way (or chill) before lifting—rhubarb filling thickens as it cools, giving neater layers. Store airtight in the fridge up to 4 days. Freezing is yes: freeze bars in a single layer, then bag for up to 2 months. For a reduced-sugar option, you can use a like-for-like sugar substitute in the filling, but expect a slightly softer set.