If you love rhubarb and date bars/matrimonial squares you'll LOVE these Rhubarb Squares. 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 to make a perfect spring dessert or snack!
Although I freeze fresh rhubarb and use it all year round, I can never seem to get enough and can't wait for it to come up in the spring. These Rhubarb Oatmeal bars were inspired by my date squares, which also make a great dessert after a lovely spring meal. Try it with my Spring Salad with Fiddleheads & Blackberry Vinaigrette. This is the best rhubarb dessert!
🍒Reader Review
"Hi, Terry. I just made this recipe. (July 7, 2024) It’s a keeper. Just the way I’d want an oatmeal rhubarb square to taste.!" ⭐⭐⭐⭐⭐
And even if you're not a rhubarb lover, you won't be able to get enough of these squares- they are totally addictive. Spring is here and that means rhubarb reason!
l only started growing my own rhubarb a couple of years ago so I get really excited when it starts to come in! Be sure to check out my other rhubarb recipes! If you love oats and rhubarb, you're sure to love my Old Fashioned Rhubarb Crumble too!
Looking for a rhubarb recipe that's a bit lighter/lower calorie? Be sure to try my Healthy Rhubarb Bread or my Healthy Rhubarb Muffins!
🥘Ingredient Notes
For this rhubarb oatmeal bar recipe, you'll need:
- Quick rolled oats. I use quick rolled oats or "quick oats" because they cook faster than regular rolled oats. Do NOT use instant oats - they will turn to mush!
- Butter. I use unsalted butter, as I like to control the salt in my butter.
- Rhubarb. You can use fresh or frozen rhubarb, but make sure you defrost and drain frozen rhubarb and measure after you have done that.
- Cornstarch. Cornstarch thickens the filling without affecting the flavor.
- Red food coloring (optional) (affiliate link) Add a little food coloring to your rhubarb compote so it looks more appetizing (red and not brown). I like to use Americolor super red (affiliate link) so I use less food coloring.
*See recipe card for full list of ingredients and quantities
📖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!
🔪Step-by-Step: How to make Rhubarb Squares
- Step 1: Filling: Cut rhubarb into ½-inch pieces. In a medium saucepan, combine rhubarb with 1 ½ cup sugar and lemon zest, on the stovetop on medium heat. Cook until tender, (about 15 minutes).
- Step 2: Combine ½ cup sugar and with cornstarch, stir into cooked rhubarb.
- Step 3: Continue cooking for an additional 10 minutes (approximately) until rhubarb is completely broken down (as shown). Cool.
- Step 4: To achieve a pink color, add food coloring, if desired.
- Step 5: Base & Topping: Preheat oven to 375 degrees F/ 190 degrees C. Spray a 9X13 pan with non-stick cooking spray. In a medium bowl, stir flour, baking soda, brown sugar, cinnamon, and oats together. Cut in cold butter into dry ingredients using a pastry cutter (or see my top tip below for an easier way to cut in butter).
- Step 6: Assembly: Pat ½ the mixture into prepared baking pan.
- Step 7:Then add rhubarb mixture on the bottom crust. Spread evenly with a rubber spatula.
- Step 8: Add the remaining flour/oat crumb topping mixture over the rhubarb layer.
- Step 9: Bake in preheated oven for 35 - 40 minutes or until lightly browned on top. Cool and cut into squares. Garnish with whipped cream and cinnamon sprinkles, 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!
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.
👪 Serving Size
This rhubarb bars recipe makes 16 square servings. However, you can cut them in half (into triangles) and get 32 servings.
You can also half, double, or triple the recipe by clicking on the serving number and selecting the number of servings you'd like. The ingredient quantities will automatically adjust. If you half the recipe, you'll need a 9-inch pan (square) and if you double it, you'll need an additional 9X13 pan.
Top tip
Keep your butter frozen (or at least very cold) and grate it into the recipe. It's easier and less messy!
❔ Recipe FAQs
To freeze rhubarb, cut off the bottom of the rhubarb stalks, wash and chop stalks into approximately ½ inch pieces. Add 3-4 cups to a large Ziplock freezer bag. Before you use it in a recipe, thaw it completely, drain off excess water, and measure it at that point.
Do you have to peel rhubarb before you cook it?
There is no need to peel rhubarb before you cook it. Rhubarb will break down when cooked, so it's no longer stringy.
You can slightly reduce the sugar in the filling, but keep in mind that rhubarb is quite tart, so cutting too much sugar may result in a sour taste. If you want to use a sugar substitute, I recommend using Monk fruit, but you'll only need to use half the amount.
Yes! Substitute the all-purpose flour with a gluten-free flour blend and ensure your oats are certified gluten-free.
If you are looking for a rhubarb square recipe or simply a way to use up your rhubarb harvest, you'll love this one!
And be sure to try my No Bake Rhubarb Cream Cheese Bars!
More Rhubarb Recipes
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📋 Rhubarb Square Recipe
Equipment
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
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 desiredDrop 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
-
- 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.
- 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!
Linda
This compote was way too sweet and I had used extra rhubarb and only 1+1/3 cups sugar! I added several apples to the mix and made a crumble from it.
Ken
These were easy to make and the recipe was very easy to follow. They turned out well, but my family and I thought they were too sweet. You lose the unique tartness of the rhubarb. I might try again with perhaps another cup of rhubarb and/or less sugar. Thank you for sharing the recipe though!!
Terri Gilson
Hi Ken,
Glad the recipe was easy to follow. Yes, you have to add quite a bit of sugar to rhubarb to balance the tart- I've never had anyone else say they were too sweet, though. I woudl definitely cut the sugar for your family!
Terri
Cindy
Do these freeze well?
Terri Gilson
Hi Cindy: Yes they do!
Fouzia Husainy
The rhubarb crumble looks tempting. Just waiting for the rhubarb season to come to make this recipe. Thank you for sharing
Asha
These are scrumptious! And sure didn't last long. Such a great way to use up my remaining frozen rhubarb before restocking this summer.
Bernice
These squares look delightful! Would you believe I still have rhubarb in the freezer and my rhubarb plant is already up. Bring on rhubarb season!
Cindy Mom the Lunch Lady
These squares remind me of the ones my Mom use to make for us growing up. They were always so yummy. I am so excited to see my rhubarb sprouting in the garden!
Judy
I love rhubarb anything! I can’t wait to try it. Looks awesomely delicious 😊
Terri Gilson
Hope you enjoy them, Judy! Please come back after you try them and leave a rating if you love them!
Terri
Vanessa
I'm adding this to the list of things that I need to make with my rhubarb this year! I can't wait! Thanks for the easy to follow directions and the tip on grating the butter.
Gail Benjamin
Hi Terry. I just made this recipe. (July 7,2024) It’s a keeper. Just the way I’d want an oatmeal rhubarb square to taste.
Terri Gilson
Glad to hear you loved it, Gail!
Terri