Rhubarb bars are the perfect treat for when rhubarb’s in season and you don’t want to fuss with making a whole pie! Tart rhubarb is balanced by sweet strawberry preserves, then baked until jammy with cinnamon-spiced oat crust.
Preheat oven to 325°F. Spray a 9 × 13-inch baking pan or dish lightly with nonstick cooking spray. LIne with parchment paper, spray again.
For the filling: In a small saucepan, mix together sugar and cornstarch. Add rhubarb, jam, and water. Stir to combine. Bring to a simmer over medium heat, stirring constantly. Reduce heat to medium low and continue to cook until thickened and rhubarb is mostly broken down, 10 minutes, or longer if the rhubarb is frozen. Mixture will be very thick. You should have about 2 ½ cups of filling. Set aside to cool slightly.
For the bars: In a large mixing bowl, combine oats, flour, brown sugar, cinnamon, and salt. Add butter and use a pastry cutter or two forks or knives to cut in the butter until the mixture is well-mixed and crumbly. It should hold together when you press it with your fingers.
Set aside 2 cups of crumb mixture. Put the remaining crumb mixture into the prepared pan and press down firmly in an even layer, using your fingers or the back of a large spoon. Bake for 10 minutes.
Remove pan from oven and carefully spoon fruit filling evenly over crust. Sprinkle with reserved crumb mixture and gently pat down with a large spoon. Put the bars back in the oven and bake for 50 minutes or until golden brown.
Cool completely. Using the parchment paper as handles, lift the bars from the pan and set on a cutting board. Using a large sharp knife, cut the bars into the desired size.
Notes
If you buy frozen rhubarb, you'll need about 21 oz.
Storage: Store bars in an airtight container for 4 to 5 days. If you want to keep them longer, refrigerate the bars for up to 7 days. To freeze the bars, wrap each bar individually in plastic wrap and then in foil. Transfer the wrapped bars into a freezer-friendly bag or container for up to 3 months. Thaw them overnight in the fridge or set them on the counter until they come to room temperature.
Recipe retested and revised 3/2024. Previously Rhubarb Cardamom Shortbread Bars.