Plum Crumble Bars

True story: I had a simple plum cake over Labor Day weekend. There was no inventive twist or clever new take on the genre, but I appreciated the deep flavor of the plums when matched with a buttery vanilla cake in this dessert in a new way.

So, I came home and went down a rabbit hole Googling dessert recipes containing plums. I wanted to see what was out there because, in truth, plums aren’t the first fruit that comes to mind when thinking of dessert. In summer, it’s peaches. In fall, apple season. But plums? This felt like new territory to me.

When I came across a Plum Cobbler Bar recipe, I liked the idea of it immediately. First of all, I made it in September, which is prime plum season (they are still in full force at the market this week, I checked). Second, I loved the play on a crumble, with that topping you can never get enough of making up not only the crumble, but the base. And, I knew that I could experiment with making it gluten-free (I was bringing it upstate to a GF hostess) without having to worry about rise like I would in a cake or bread.

I ended up cutting out a full cup of sugar from the original recipe – I truly don’t think it needs it. I also used a combination of gluten-free flour and oat flour (both from Bob’s Red Mill), and the oat flour adds a nice nuttiness to the base and topping. I substituted dark brown sugar for further depth of flavor, but if you only have regular brown sugar, that will do too.

Another plus with this recipe is that you can keep the crumble part, and rotate out the fruit you use based on what’s in season. I personally think that pears would make a phenomenal jam in this recipe, perhaps even paired with a hint of nutmeg. I also think that apricots would be delightful in summer. Keep this one in your arsenal. Play around with subbing in different fruits, and let me know how it goes 🙂

Plum Crumble Bars


  • 2 ¼ pounds plums, pits removed and roughly chopped (about 6 cups)
  • ½ cup plus 1/3 cup granulated sugar
  • ¼ cup cornstarch
  • 2 teaspoons vanilla extract
  • 3 cups old-fashioned oats
  • 2 ½ cups gluten-free flour
  • ¾ cup oat flour
  • 1 ½ cups dark brown sugar
  • 1 teaspoon baking powder
  • 1 teaspoon coarse kosher salt
  • 1 teaspoon ground cinnamon
  • 1 ½ cups unsalted butter (3 sticks), melted


  1. In a large pot, combine plums and a scant 1/2 cup of granulated sugar. Heat over medium-low heat, stirring occasionally, until fruit releases juices and becomes very tender, 12 to 15 minutes. 
  2. Break up plums with your wooden spoon as they cook over medium-low heat, stirring occasionally, until mixture thickens and reduces by about half, about 10 minutes. You should end up with about 3 1/2 cups of plum jam. 
  3. In a small bowl, whisk remaining 1/3 cup granulated sugar with cornstarch to combine. Whisk sugar-cornstarch mixture into jam and cook, stirring occasionally, until it simmers. Simmer for 1 minute, stirring well to prevent scorching. Stir in vanilla extract, and cool plum mixture to room temperature.
  4. Heat oven to 350 degrees, and line a 9-by-13-inch pan with parchment paper with overhang on all sides. In a large bowl, combine oats, gluten-free flour, oat flour, brown sugar, baking powder, salt and cinnamon. Add melted butter and stir until the mixture forms streusel-like crumbs – it may be easier to do this with your hands. 
  5. Press 2/3 of crumb mixture into an even layer at bottom of prepared pan. Spread cooled plum jam in an even layer over crust, then sprinkle remaining crumb mixture evenly over top of jam.
  6. Bake until jam bubbles at edges and streusel is lightly browned, 45 to 55 minutes. Cool completely before slicing into pieces – I like making smaller ones, personally.

Original recipe can be found here.

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