📋 Rhubarb Square Recipe

rhubarb square on a white plate, with glass dish of more rhubarb squares in the background

4.75 from 8 votes

These Rhubarb Squares, also known as Rhubarb Crumble Bars, have a delicious rhubarb compote filling that's the perfect balance between sweet and tart, nestled between a scrumptious oatmeal base and topping. They are ideal for using up an abundance of rhubarb and make a perfect spring dessert or snack!

Course Dessert, Snack

Cuisine American, Canadian

Keyword bar, rhubarb, squares

Special Diet Vegetarian

Prep Time 30

Cook Time 36

Total Time 1 5

Servings servings

Calories 338kcal

Author Terri Gilson

Equipment

9x13 glass pan with lid

Ingredients

Filling

4 cups rhubarb
2 teaspoon lemon zest
2 cups sugar
2 ¾ tablespoon cornstarch
Drop red food colouring optional

Base & Topping

1 ½ cups all-purpose flour
1 cup brown sugar
1 ¾ cups rolled oats
1 cup cold unsalted butter
¼ teaspoon baking soda
½ teaspoon cinnamon

US Customary - Metric

Instructions

Filling

Cut rhubarb into ½ inch pieces. In a medium saucepan, cook rhubarb with 1 ½ cup sugar and lemon zest, on stovetop on medium heat, until tender, (about 15 minutes).
4 cups rhubarb, 2 teaspoon lemon zest, 2 cups sugar
Combine ½ cup sugar and with cornstarch, stir into cooked rhubarb.
2 ¾ tablespoon cornstarch
Continue cooking for about 5-10 additional minutes, until rhubarb has broken down. Cool
To achieve a pink color, add food colouring, if desired
Drop red food colouring
Preheat oven to 375 degrees F/190 degrees C. Spray a 9X13 pan with non-stick cooking spray.

Base

In a large mixing bowl, stir flour, baking soda, brown sugar, cinnamon, and oats together. Cut in cold butter.
1 ½ cups all-purpose flour, 1 cup brown sugar, 1 ¾ cups rolled oats, 1 cup cold unsalted butter, ¼ teaspoon baking soda, ½ teaspoon cinnamon
Pat ½ the mixture into the bottom of the pan.
Then add rhubarb filling mixture on top. Spread evenly with a rubber spatula.
Add remaining flour/oat crumb topping mixture over rhubarb layer.
Bake in preheated oven for 35 - 45 minutes or unti lightly browned.
Cool and cut into squares. Serve with a dollop of whipped cream and a sprinkle of cinnamon, if desired. Hint: It's important to wait until rhubarb squares are completely cooled before cutting, otherwise they will fall apart. You can put them in the freezer to speed up the process!

Notes

Expert Recipe Tips:

- Use a glass pan or coated pan for best results. Rhubarb is acidic – you shouldn't cook rhubarb in aluminum, copper, or iron pans that react. In metal pans, rhubarb turns brownish and the pan discolors.
- Use Quick Oats for the Best Texture. Quick oats provide the perfect balance between chewiness and crunch. If using old-fashioned rolled oats, pulse them in a food processor a few times to break them down. Avoid instant oats, as they can become mushy.

- Freeze the Butter for Easy Mixing. For the best crumb texture, keep your butter very cold. Grating frozen butter into the dry ingredients makes it easier to incorporate evenly without overmixing.

- Don’t Skip the Cornstarch. Cornstarch thickens the rhubarb filling, preventing it from being too runny. Without it, your squares might turn out too soft and messy.

- Let the Bars Cool Completely Before Cutting. If you cut them while they’re still warm, they will likely fall apart. Speed up the cooling process by placing them in the fridge or freezer.

- Adjust the Sweetness Based on Your Rhubarb. Rhubarb can vary in tartness. Taste your cooked filling before assembling and add a little more sugar if needed.

- Optional: Enhance the Color Naturally. If you prefer to skip food coloring, adding a handful of chopped strawberries to the rhubarb filling can give it a more vibrant red hue.

- Make It Ahead. These bars store well! You can bake them a day ahead and refrigerate them overnight for the best texture.

🌡️Storage

Store these rhubarb oatmeal bars in the fridge in an airtight container for up to 4 days (if they last that long!) and freeze them for up to 3 months in a sealed container.

Variations & Substitutions:

Lemon zest - you can use 2 teaspoons of lemon juice instead or use orange zest

Rolled Oats- if you only have old-fashioned/regular rolled oats you can put them in your food processor and pulse them a couple of times to break them down and use them as a substitute for quick rolled oats.

Sugar - some readers find this too sweet. You can start with less sugar in the filling, and add more at the end to your desired sweetness. Neither I nor my family likes things overly sweet and we found this perfect!

Nutrition