If you have rhubarb growing in your garden, this is a recipe you’ll want to make every spring and summer. These Fresh Milled Flour Rhubarb Crumble Bars have a buttery oat crumble made with freshly milled soft wheat berries and a simple sweet-tart rhubarb filling. They’re easy to put together, perfect for sharing, and a wonderful way to make the most of rhubarb season.

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Fresh Milled Flour Rhubarb Crumble Bars arranged on parchment paper with a buttery oat crumble topping.

Why You’ll Love These Fresh Milled Flour Rhubarb Crumble Bars

Made with freshly milled whole-grain flour for incredible flavor and nutrition.
Perfect balance of buttery, sweet, and tart.
Quick and easy to put together.
One dough becomes both the crust and crumble topping.
Great way to use fresh garden rhubarb.

Close-up of a Fresh Milled Flour Rhubarb Crumble Bar showing the buttery crust, tender rhubarb filling, and crisp oat crumble topping.

Ingredients for Fresh Milled Rhubarb Crumble Bars:

Butter: I always use salted butter in my baking because that’s what I keep on hand, but unsalted butter works just as well. If possible, choose a high-quality butter like Kerrygold or another grass-fed variety for the richest flavor.
Brown Sugar: Brown sugar adds moisture, chewiness, and a caramel-like flavor that pairs perfectly with tart rhubarb.
Granulated Sugar: A little white sugar sweetens both the crumble and the filling, balancing rhubarb’s natural tartness without overpowering it.
Vanilla Extract: A tablespoon of vanilla gives the buttery crumble a richer flavor. I always recommend using pure vanilla extract if you have it.
Soft Wheat Berries: Soft wheat is my favorite for desserts like these because it’s naturally lower in protein, producing a softer, more tender crumb. I used soft white wheat for this, but einkorn, spelt, or kamut would all work well.
Old-Fashioned Oats: Use old-fashioned rolled oats. They give the crumble its hearty texture and crisp topping. Quick oats absorb moisture differently and won’t produce the same result.
Rhubarb: Fresh rhubarb is wonderful when it’s in season. Chop it into small, even pieces so it bakes evenly. Frozen rhubarb works great too—just thaw first and strain the excess liquid.
Arrowroot Powder: Arrowroot powder thickens the rhubarb filling so it slices beautifully once cooled. If you don’t have arrowroot, cornstarch is an easy one-to-one substitute.
Salt: Don’t skip the salt! It brings all of the flavors together and helps balance the buttery crust with the tart rhubarb.
Baking Soda: Baking soda helps give the crumble a lighter texture and encourages beautiful golden browning as it bakes.

How to Make Fresh Milled Flour Rhubarb Crumble Bars

Preheat the oven to 350°F. Grease or line a 9×13-inch baking dish with parchment paper.
Weigh and mill your wheat berries on the finest (or lowest) setting on your grain mill for the finest flour.
In a medium bowl, combine the freshly milled flour, oats, salt, and baking soda.
In a stand mixer or large bowl, combine the melted butter, white sugar, brown sugar, and vanilla extract.
Add the flour and oat mixture to the butter mixture and mix until incorporated.
Press two-thirds of the mixture firmly into the prepared pan to form the crust; I weigh my entire dough, then figure out how many grams 2/3rds are, to be precise.
In a separate bowl, toss the chopped rhubarb with sugar and arrowroot powder until evenly coated.
Spread the rhubarb mixture out evenly over the crust.
Sprinkle the remaining crumble mixture evenly over the top.
Bake for 50–55 minutes, or until the crumble is golden brown and the filling is bubbling around the edges.
Let the bars cool completely before slicing.

How to Store Rhubarb Crumble Bars

Store covered at room temperature for up to 3 days, or refrigerate for up to 5 days.

Separate the bars with parchment paper and freeze up to 3 months. Thaw overnight in the refrigerator before serving.

Freshly Milled Rhubarb Crumble Bars on parchment paper with golden oat crumble and sweet-tart rhubarb filling.

Tips for the Best Fresh Milled Flour Rhubarb Crumble Bars

Chop the rhubarb into small, even pieces for the best texture.
Line your baking dish with parchment paper so the bars are easy to remove.
For an easy way to divide the crust and crumble, weigh the finished mixture on a kitchen scale and calculate 2/3 of the total. For example, my mixture weighed 1,200 grams, so I pressed 800 grams into the pan for the crust and reserved the remaining 400 grams for the crumble topping.
Allow the bars to cool completely before cutting—they slice much cleaner once the filling has set.

Rhubarb Crumble Bar Variations

Swap out 2 cups of rhubarb for strawberries for classic strawberry rhubarb bars.
Mix 1 teaspoon cinnamon into the crumble for a warm flavor.
Stir in ½ to 1 cup chopped pecans or walnuts for extra crunch.
Add a tablespoon of fresh lemon juice to the filling for extra brightness.
Love tart desserts? Reduce the sugar slightly.

Freshly Milled Rhubarb Crumble Bars with a buttery crust, sweet-tart rhubarb filling, and crisp oat crumble topping.

FAQ

Yes. Use the same amount of cornstarch as a direct substitute.

Absolutely. Just thaw it first and drain away any excess liquid.

Soft wheat produces a tender, buttery crumble that works the best in dessert bars, so soft white, spelt, einkorn, or kamut.

No. Simply wash, trim the ends, and chop. Be sure to discard the leaves, as they are not edible.

Similar Recipes

Equipment

Grain mill
Kitchen scale
9×13" baking dish
Parchment paper

Ingredients

For the Crust & Crumble

1 cup melted butter
1 cup packed brown sugar
1 cup granulated sugar
1 tablespoon vanilla extract
280g soft wheat berries white, spelt, einkorn, etc.
2 cups old-fashioned oats
1 teaspoon salt
1 teaspoon baking soda

For the Filling

4¼ cups chopped rhubarb
⅔ cup granulated sugar
2 tablespoons arrowroot powder or cornstarch

Instructions

Preheat the oven to 350°F. Grease or line a 9×13-inch baking dish with parchment paper.
Weigh and mill your wheat berries on the finest (or lowest) setting on your grain mill for the finest flour.
In a medium bowl, combine the freshly milled flour, oats, salt, and baking soda.
In a stand mixer or large bowl, combine the melted butter, white sugar, brown sugar, and vanilla extract.
Add the flour and oat mixture to the butter mixture and mix until incorporated.
Press two-thirds of the mixture firmly into the prepared pan to form the crust; I weigh my entire dough, then figure out how many grams 2/3rds are, to be precise.
In a separate bowl, toss the chopped rhubarb with sugar and arrowroot powder until evenly coated.
Spread the rhubarb mixture out evenly over the crust.
Sprinkle the remaining crumble mixture evenly over the top.
Bake for 50–55 minutes, or until the crumble is golden brown and the filling is bubbling around the edges.
Let the bars cool completely before slicing.

Notes