Rhubarb Oatmeal Bars

Rhubarb Oatmeal Bars are sweet and tart with a brown sugar oatmeal cookie crust, gooey fruit filling, and a buttery oatmeal crumble topping. This delicious cookie bar recipe comes together in minutes with fresh or frozen rhubarb.

Here in Minnesota, rhubarb season is our first taste of spring -- signaling it's time to make alllll the rhubarb recipes. Anyone with a rhubarb patch usually has an abundance of rhubarb and by mid-summer, the entire state smells like rhubarb pie. 

This great recipe for old fashioned oatmeal rhubarb bars was inspired by family favorite recipes I found in our grandmothers' recipe boxes -- it was right past the Coconut Dream Bars and Hello Dolly Bars.

This sweet dessert has a brown sugar oatmeal cookie base, gooey, sweet, and tart rhubarb fruit filling with a hint of orange, and a crunchy oat crumble topping. These old fashioned rhubarb bars are the perfect dessert to enjoy cold with a hot cup of coffee, or warmed up topped with a scoop of vanilla ice cream. 

You're going to love these

• Super easy to make with simple ingredients
• You can make these rhubarb oatmeal bars with fresh or frozen rhubarb 
• Orange zest and juice in the rhubarb filling makes it taste extra summery
• The brown sugar oatmeal cookie crust and buttery crumble topping is to-die-for

Ingredients

• Old fashioned rolled oats. Old-fashioned oats, aka, rolled oats, are the best choice for baking because they will keep their texture when baked. 
• Brown sugar. I always use dark brown sugar, but light brown sugar will work just fine, too. 
• Cinnamon. One teaspoon of cinnamon adds just the right amount of warm flavor to the cookie base and crumb topping.
• Salt. A little bit of salt in the oatmeal mixture and rhubarb filling helps to enhance the flavor. 
• Melted butter. Since you're already adding salt, use unsalted butter. 
• Rhubarb. You can make these bars with fresh rhubarb or frozen, unthawed rhubarb. You may be able to find frozen chopped rhubarb in grocery stores.
• Orange juice and zest. Citrus enhances the flavor of the rhubarb and brings another fresh flavor to these delicious old fashioned rhubarb bars. You can also use lemon juice and lemon zest. 
• Corn starch. A little cornstarch thickens the rhubarb mixture as it bakes. 

Step-by-step instructions

Step 1

Heat oven to 350 degrees and line a 9x9 pan or baking dish with parchment paper to make removing the bars from the pan easier.

Step 2

In a large bowl, add the all purpose flour, oats, brown sugar, cinnamon, baking powder and salt. Use a spoon to break up the brown sugar and stir the oat mixture together. 

Step 3

Add the melted butter and stir until it comes together like clumps of wet sand. 

Step 4

Pat ⅔ of the mixture into the bottom of the pan. Bake the cookie crust for 10 minutes.

Step 5

In a medium bowl, combine rhubarb, sugar, cornstarch, orange juice, orange zest, and salt together.  

Step 6

Arrange the fruit mixture over the bottom crust. Crumble the remaining crumb mixture over the top. 

Step 7

Bake for 30-40 more minutes or until the top is golden brown. 

Dig in right away to enjoy a warm and gooey rhubarb bar with a scoop of ice cream or chill them in the refrigerator until they're set up.

Add a dusting of powdered sugar on top of the bars, if you like.

Expert Tips

• If you use frozen rhubarb, do not thaw it first. 
• For a warm rhubarb crisp-like dessert, go ahead and dig into these oatmeal rhubarb crumble bars right away. 
• For a firmer bar-like consistency, chill them in the refrigerator. Don't worry, the fruit filling will still be nice and gooey!

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