These strawberry rhubarb bars are sturdy enough to eat with your hands, thanks to a thick, but soft & chewy oatmeal layer. The filling has a fresh, bright fruity flavor that tastes exactly like you'd expect strawberries and rhubarb to taste like.
The oatmeal crust comes together quickly, thanks to the use of melted butter. The filling is just as easy to make - simply mix chopped strawberries, rhubarb sugar, cornstarch, and lemon juice in a bowl, then spread it onto the crust.
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I tested out some fillings to find the best ones. After settling on the ratios between the strawberries and rhubarb, I focused on how to cook the filling. I made two batches with the exact same ingredients and ratios.
- Precooked: simmered fruit and reduced into a jammy texture for 10 minutes on the stove top before baking in the oven
- Fresh: added uncooked fruit to the oatmeal bar base before baking in the oven
I expected the precooked jammy filling to make the best bars, working on the assumption that it would concentrate the flavor. It turned out the opposite was true. The fresh, uncooked fruit had much more flavor in the finished strawberry rhubarb oatmeal bars.
After some research, it turns out that strawberries quickly lose their aromatic compounds when heated, which is a large source of their flavor. [1,2]
Recipe
Ingredients
OATMEAL CRUST
- 1 cup all-purpose flour (130 grams / 4.5 ounces)
- 1 ⅔ cup quick oats 140 grams / 5 ounces
- 1 teaspoon baking powder
- 1 teaspoon cinnamon
- ¼ teaspoon salt
- ½ cup brown sugar 100 grams / 2.5 ounces
- 1 large egg
- ⅓ cup melted butter 70 grams / 2.5 ounces
- ¼ cup maple syrup 80 grams / 2.8 ounces
STRAWBERRY RHUBARB FILLING
- 2 cups diced strawberries Dice ¼" pieces. 283 grams / 10 ounces
- 1 ½ cups diced rhubarb Dice ¼" pieces. about 200 grams / 7 ounces
- ⅓ cup granulated sugar 67 grams / 2.4 ounces
- 1 tablespoon lemon juice fresh or bottled
- 1 tablespoon corn starch
Instructions
MAKE OATMEAL CRUST & CRUMBLE TOPPING
- PREPARE: Preheat oven to 350℉. Line a metal 8x8 inch baking pan with parchment paper, leaving two sides to overhang like handles. This lets you lift the bars out to easily cut them. (You can use a 9x9 but might need more oatmeal crumble for the top, instructions below).
- MEASURE DRY: In a large bowl measure out flour, oats, baking powder, and spices. Stir to combine. Add brown sugar.
- ADD WET: Add in melted butter, maple syrup, and egg. Stir to combine.
- PRESS IN CRUST: Take 1 ½ cups of the mixture and press it evenly into the pan. You should have about ½ cups of oatmeal mixture remaining for the top.
- LEFTOVER OATMEAL CRUMBLE: It might not look like you have much left, but you only need about a ⅓ cup to dabble over the top of the fruit filling. If you used a 9x9 pan, you might need more. To make more, mix in 1 tablespoon each of: melted butter, maple syrup, brown sugar, and flour PLUS 3-4 tablespoon quick oats, and a pinch of salt.
STRAWBERRY RHUBARB FILLING
- MIX FRUIT: add the diced strawberries and rhubarb to a mixing bowl along with lemon juice and stir to coat.NOTE: If your strawberries are really bland, feel free to add a ½ teaspoon of vanilla or almond extract to the bowl. Otherwise, don't add it so you can preserve the natural fresh fruit flavor.
- ADD SUGAR & CORNSTARCH: in a small bowl, stir together sugar and cornstarch. You want the cornstarch to be evenly distributed and not clump. Pour sugar+cornstarch mixture over the fruit. Stir to coat.
- POUR OVER CRUST: Pour the strawberry rhubarb filling over the oatmeal crust. Spread out evenly. Add little pieces of the crumble topping, dotted all over the top of the filling.
BAKE AT 350℉ for 20-25 minutes
- Bake the bars for 20-25 minutes. The top crumble layer will be browned and the filling will look softened and a little jammy. Let cool before slicing (or they can fall apart).
STORAGE
- These bars last on the counter for 2-3 days, or in the fridge for 5 days. They crumble topping might get a little soft in the fridge, but it honestly still tastes fantastic!
Notes
Nutrition
Testing the strawberry rhubarb filling
This spring, I was on a mission to make the best strawberry rhubarb oatmeal bar recipe. I already had a great oatmeal base from my fresh fig oatmeal bar recipe, so all I had left to do was test out some fillings.
I wanted the filling to taste as much like the fresh fruit as possible - it should be sweet and tart and thick. I wanted the strawberry-rhubarb flavor to be dominant and not get washed out by the oatmeal crust.
I settled on a ratio of just slightly more strawberries than rhubarb so I could keep the sugar in check. Adding more rhubarb often requires more sugar. While less sugar makes the bar healthier, that wasn't my motivation. Sugar often makes desserts overly sweet and overpowers some of the fruits' natural flavor.
I mentioned earlier that I tested the strawberry rhubarb filling a couple of different ways:
- Precooked: I simmered the strawberries and rhubarb with the sugar, cornstarch, and lemon juice on the stove top for 10 minutes. I let it cool for 5 minutes then poured it onto the unbaked oatmeal crust and baked it in the oven.
- Fresh: I mixed the chopped strawberries, rhubarb, sugar, cornstarch and lemon juice in a bowl. I poured that on top of the unbaked oatmeal crust and baked it in the oven.
The amount of each of the ingredients was exactly the same between the two tests. The idea was to determine if precooking the filling resulted in a tastier bar.
Flavor
It turns out the fresh filling baked up with significantly more flavor. Every taste tester declared the fresh-fruit version their favorite almost immediately because the of the obvious flavor difference.
After some research, I found out that strawberries definitely lose their aromatic compounds when cooked. I went down the internet rabbit hole and found there are a lot of recipes for minimally cooking strawberries in desserts and jams.
In fact, there's even a fresh strawberry jam recipe that pours boiling water (mixed with pectin) over mashed, but uncooked strawberries. The jam is then stored in the freezer to avoid cooking them in a water bath canner.
The strawberries in the filling for these bars are baked, but minimally compared to precooking on the stove top. Baking is also gentler than boiling. That's why they maintain a much brighter, fruity flavor.
Texture
The fresh strawberry-rhubarb filling also had the better texture. It was both light and jammy. The precooked filling was more of a thick jam that turned a little sticky on the edge pieces.
Presentation
The bars with the fresh fruit filling also looked prettier with a stunning bright-red color. It was also obvious that the bars were made with fresh strawberries and rhubarb since you could still see some of the actual chopped pieces. They baked up taller as well.
The precooked bars look darker (which is pretty too), but they could have been made with a store bought jam based on the appearance. In essence, they were, since the filling was cooked down into a jammy consistency.
Working with fresh strawberries & rhubarb
Rhubarb season starts in early spring, with strawberries ripening shorty after. Their overlapping seasonality is one of the main reasons for their popular pairing - not to mention their flavors are quite complimentary.
Dice both the strawberries and rhubarb small. Cut them small enough to cook down in a short amount of time, since they are added to the oatmeal base raw. The photo above shows the size of the fruit I diced.
Rhubarb
Rhubarb grows best in colder climates where the ground freezes in winter. In those regions, you can find rhubarb at farmers markets and often grocery stores.
In warmer regions, it can be pretty difficult to find fresh rhubarb. Keep tabs on the grocery stores throughout spring and early summer. Whole Foods is a good bet, and there are reports of the big grocery chains selling rhubarb as well.
When you buy rhubarb, it should be sturdy (not limp) and free of bruises. Good rhubarb has similar characteristics as celery when picking it out. The color of the stalks is actually not a good indicator of flavor. The color is more indicative of the variety than it's stage of ripeness.
Store rhubarb in the fridge for a week, possibly two if you bought it really fresh. If it gets limp in the fridge, you can still use it in this recipe (and in most baking recipes). Just make sure it is still in good condition with no signs of decay or off odors.
Don't eat rhubarb leaves, they are poisonous.
Strawberries
Fresh strawberries that are perfectly ripe for the season are obviously fantastic for these strawberry rhubarb bars. However, this is one of those recipes that can rescue bland strawberries.
If you end up with bland strawberries, you can still use them as directed. The sugar sweetens them back up and the rhubarb adds some extra flavor and acidity. For even more flavor, you can add in a teaspoon of vanilla or almond extract and cinnamon to the bowl when mixing the strawberries and rhubarb together.
Oats: old-fashioned vs quick oats
Old-fashioned oats are also called rolled oats. To make them, manufacturers steam and then flatten the oats. They are less processed, retaining more of their flavor, shape, and texture when cooked.
Quick oats are also called instant oats. Instead of being steamed, they are actually precooked, then dried and flattened. This allows them to be reheated quite quickly from simply mixing with hot water for a bowl of oatmeal. Compared to old-fashioned oats, these have slightly less flavor and don't maintain their texture well once baked.
Steel cut oats are hulled oat grains, which are then cut and toasted - they are not cooked or steamed like the previously mentioned oats. Steel cut oats are rarely used in baking because they take too long to soften and absorb liquid.
Old-fashioned oats are popular in cookie recipes and baked goods where you want to see and taste distinct oats. Quick oats are better for adding bulk or texture that melts into the background.
I use quick oats for these strawberry rhubarb oatmeal bars because they make a sturdier base that can be picked up by hand without falling apart. I've made these bars with both quick oats and old-fashioned oats - the ones with quick oats definitely came out sturdier.
That said, rolled old-fashioned oats do work. If you want to see a recipe for strawberry rhubarb bars using rolled oats, check out this one from Cooking Classy. You can even see how the oats held their shape after cooking in her photos.
Another option would be to make these bars with half of each - I'll give that a try next and report back. Alternatively, you could make a separate oat topping for the bars using old-fashioned oats for a more pronounced flavor and texture.
More recipes & resources
The oatmeal crust I used for these strawberry rhubarb bars is the same one I used for these homemade fig bars that use fresh figs (not preserves or dried figs). They taste like fall - with cinnamon, maple syrup, and deep brown sugar flavors.
I also have a collection over over 75 strawberry recipes with really fun twists on strawberry shortcake, salads, and preserving. The rhubarb recipe collection mixes fresh stalks with other seasonal fruit as well as savory recipes paired with meat.
Also follow me on Pinterest for more seasonal recipes that I make and save from other sources.
Jackie says
The bars had such a good flavor and everyone loved them. Next time I'm making a double batch so I have leftovers.
Veronica T says
I'm so glad they were a hit! Grab some more rhubarb while it's still in season 🙂