There’s something about rhubarb season that makes me want to head straight to the kitchen and bake something cozy and sweet.
These rhubarb oat bars are my go-to treat when I’ve got fresh stalks on hand and a craving for something simple, tangy, and satisfying.
With a buttery oat crumble, a soft, jammy rhubarb center, and just the right balance of sweet and tart, they’re the kind of bar you’ll want to keep stocked in your fridge all spring long.
I started making these bars when I had a bunch of garden rhubarb to use up—and now, they’re a yearly must-bake.
They’re sweet, a little tart, and packed with that cozy oat crumble we all love.
This easy rhubarb oat bar recipe is perfect for a quick dessert, an afternoon snack, or even a breakfast treat (no judgment here).
No mixer, no fuss—just simple pantry ingredients and fresh rhubarb baked into soft, buttery layers.
Whether you’re new to baking with rhubarb or already a fan, this recipe is a keeper.
How To Make Rhubarb Oat Bars?
Recipe Overview
These Rhubarb Oat Bars start with a buttery oat crust, filled with a quick homemade rhubarb jam, and topped with a golden oat crumble and cinnamon sugar.
- Prep Time: 15 minutes
- Cook Time: 40 minutes
- Total Time: 55 minutes
- Cuisine: American
- Course: Dessert, Snack
- Difficulty: Easy
- Yield: 12 bars
- Calories: Around 210 per serving
Equipment
- 8×8 inch baking dish
- Mixing bowls
- Saucepan
- Spatula
- Measuring cups & spoons
- Knife and cutting board
Ingredients
Rhubarb Filling:
- 4 cups chopped rhubarb (fresh or frozen)
- 1/2 cup sugar
- 1 tbsp water
- Generous squeeze of lemon juice
Oat Bar Crust & Topping:
- 1 1/4 cups all-purpose flour
- 1 1/4 cups quick oats
- 2/3 cup sugar
- 1/4 tsp kosher salt
- 1/2 cup butter, melted
Sugar Topping:
- Cinnamon + sugar mix (to sprinkle on top)
Ingredient Notes
- Rhubarb: Both fresh and frozen work. No need to thaw if using frozen—just cook it a little longer.
- Quick Oats: These work best here. Old-fashioned oats are a bit too thick for the texture we want.
- Butter: Melted butter makes mixing easier and gives the bars a rich, tender bite.
- Lemon Juice: Brightens up the rhubarb and balances the sweetness.
- Cinnamon Sugar: Gives the topping a little warmth and crunch. Totally worth it.
Direction
Step 1: Make the Rhubarb Filling
In a saucepan, combine the rhubarb, sugar, water, and lemon juice. Bring to a simmer over medium heat. Cook for about 10–12 minutes, stirring occasionally, until the rhubarb breaks down and thickens. Set it aside to cool slightly.
Tip: Keep stirring gently so it doesn’t stick to the bottom of the pan. It should look like a loose jam.
Step 2: Mix the Crust and Topping
In a bowl, stir together the flour, oats, sugar, and salt. Pour in the melted butter and mix until everything’s moistened. It’ll look crumbly, but should hold together when pressed.
Step 3: Assemble
Press about 2/3 of the oat mixture into a greased 8×8 pan to form the crust. Spread the rhubarb filling evenly over the crust. Sprinkle the remaining oat mixture on top.
Finish with a light dusting of cinnamon sugar.
Step 4: Bake
Bake at 350°F (175°C) for 35–40 minutes, until the top is golden and the filling bubbles at the edges.
Step 5: Cool and Cut
Let the bars cool completely in the pan before slicing. They’ll set up as they cool, so don’t rush this part.
Nutrition
- Calories: 210
- Fat: 9g
- Carbs: 30g
- Sugar: 18g
- Fiber: 1g
- Protein: 2g
Serving Suggestions
I love serving these chilled, especially in warm weather. They’re great with a scoop of vanilla ice cream or a drizzle of strawberry jam. You could even pack them in a lunchbox or picnic basket.
How Should I Store Leftover Rhubarb Bars?
Keep them in an airtight container in the fridge for up to 4 days. You can also freeze them in a single layer, then stack with parchment between layers. Let them thaw in the fridge or at room temp before serving.
Can I Make These Bars Gluten-Free?
Yes! Just use a gluten-free flour blend that substitutes 1:1 for regular flour, and make sure your oats are labeled gluten-free.
What Kind of Oats Do You Use in the Crust and Topping?
Quick oats are the way to go. They mix into the dough easily and bake into a tender, chewy texture. Avoid steel-cut or old-fashioned oats—they don’t blend well in this kind of recipe.
Should I Use Fresh or Frozen Rhubarb?
Both work fine! Fresh rhubarb is ideal when it’s in season, but frozen rhubarb is a great backup. No need to thaw it—just toss it in the pot and cook it down a little longer.
FAQ
Can I Swap The Rhubarb For Other Fruit?
Sure! Strawberries or raspberries work great, especially if you want to lean into that strawberry lemon bars idea.
Can I Double This Recipe?
Yes—use a 9×13 pan and extend the baking time by 5–10 minutes.
Can I Make Them Less Sweet?
You can reduce the sugar a bit in the filling, but keep it in the crust so it holds together.
Final Thoughts
If you’ve got rhubarb in the fridge, this is one of the easiest ways to use it up. These bars are cozy, tart, buttery, and easy to make in one bowl. If you try them,
I’d love to hear how it goes! Leave a comment, ask a question, or tag me in your baking photos—I’m always happy to see what you’re making.
Rhubarb Oat Bars
Equipment
- 8×8-inch baking dish
- Mixing bowls
- Saucepan
- Spatula
- Measuring cups & spoons
- Knife and cutting board
Ingredients
Rhubarb Filling:
- 4 cups chopped rhubarb fresh or frozen
- 1/2 cup sugar
- 1 tbsp water
- Generous squeeze of lemon juice
Oat Bar Crust & Topping:
- 1 1/4 cups all-purpose flour
- 1 1/4 cups quick oats
- 2/3 cup sugar
- 1/4 tsp kosher salt
- 1/2 cup butter melted
Sugar Topping:
- Cinnamon + sugar mix to sprinkle on top
Instructions
Step 1: Make the Rhubarb Filling
- In a saucepan, combine the rhubarb, sugar, water, and lemon juice. Bring to a simmer over medium heat. Cook for about 10–12 minutes, stirring occasionally, until the rhubarb breaks down and thickens. Set it aside to cool slightly.
- Tip: Keep stirring gently so it doesn’t stick to the bottom of the pan. It should look like a loose jam.
Step 2: Mix the Crust and Topping
- In a bowl, stir together the flour, oats, sugar, and salt. Pour in the melted butter and mix until everything’s moistened. It’ll look crumbly, but should hold together when pressed.
Step 3: Assemble
- Press about 2/3 of the oat mixture into a greased 8×8 pan to form the crust. Spread the rhubarb filling evenly over the crust. Sprinkle the remaining oat mixture on top.
- Finish with a light dusting of cinnamon sugar.
Step 4: Bake
- Bake at 350°F (175°C) for 35–40 minutes, until the top is golden and the filling bubbles at the edges.
Step 5: Cool and Cut
- Let the bars cool completely in the pan before slicing. They’ll set up as they cool, so don’t rush this part.
