Name: Old-fashioned rhubarb crisp bars (vegan)
Prep time: 15 min
Cook time: 30 min
Total time: 45 min
Ingredients: 3 cups chopped rhubarb (roughly 3/4-inch pieces); 2 cups sugar (divided); 2 Tablespoons cornstarch; 1/4 cup water; 1 teaspoon vanilla extract; 1 1/2 cups rolled oats; 1 1/2 cups all-purpose flour; 1 Tablespoon molasses; 1/2 teaspoon baking soda; 1 cup non-dairy butter; 1/2 cup roasted pistachios

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Rhubarb crisp bars are a well-loved family favorite. A crispy streusel-type oat layer surrounds tart and tangy rhubarb filling.

These satisfying dessert bars are delicious on their own or served alongside vanilla ice cream. Great for holidays, potlucks, family get-togethers, and picnics.

Old-fashioned rhubarb bars are a classic dessert that satisfies every time.

My mom started making them back in the early 1970’s. She saw a recipe in the newspaper that caught her eye, and clipped it out.

They’ve been in regular rotation in our family ever since.

The yellowed and well-worn recipe calls for ingredients like “oleo” and “nutmeats.” The instructions are slight and a little vague. So over time, the recipe has been modified and changed – first by my mom, and then by me.

While rhubarb is still in season, I knew I needed to share this easy updated recipe with you.

It’s made with top and bottom layers of sweet and chewy oatmeal crisp, dotted with crunchy pistachios. Then sandwiched between the layers is gooey, tart, and tangy rhubarb. There’s a dash of vanilla to make those dessert flavors pop.

Finally, the rhubarb crisp is cut into bars. They can be enjoyed on their own or alongside vanilla ice cream for a hot & cold treat.

Make a batch of rhubarb squares for your next potluck, cookout, family get-together, or holiday. (They’re perfect for spring and summer holidays like Memorial Day, Labor Day, and the Fourth of July.)

This dessert also freezes well in individual bars. Plan to pluck one out during winter months when you need a little taste of summer.

In this post:

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Ingredients
Step by step instructions
Make it your own
Serving ideas
Storage instructions
📖 Recipe

Ingredients

Here are the ingredients you will need to make this recipe.

Rhubarb: Fresh is best, but you can also use frozen rhubarb for this recipe. If there’s any frost on your frozen rhubarb, quickly rinse it off before adding it to the pot while it’s still frozen.

(Need to know how to freeze rhubarb? Follow the directions in this easy Instagram reel.)

Sugar: The original recipe used both white and brown sugar. However, to keep things easy, I just use white sugar and then add molasses (which is what turns white sugar brown).

If you’d prefer, you can omit the molasses, and use white sugar in the rhubarb sauce and brown sugar in the oat crisp mixture. You’ll need one cup of each.

Cornstarch: Cornstarch thickens the rhubarb sauce, so that the bars aren’t runny. You want them to form into cohesive bars.

Vanilla: Use pure vanilla extract, not imitation vanilla.

Rolled oats: They’re also called old-fashioned oats. They can be replaced with quick oats, but do not use stoneground or steel cut oats. They won’t work in this recipe.

Flour: Choose all-purpose flour.

Molasses: This thick syrup is added to white sugar to make brown sugar. I use it in this recipe, so that two different types of sugar aren’t needed.

Baking soda: This is added to the oatmeal layer to help with browning and crisping.

Pistachios: Choose shelled and roasted pistachios. They can be salted or unsalted. If you’d prefer, replace them with an equal amount of your preferred chopped nuts. If you don’t like or can’t eat nuts, simply leave them out.

Non-dairy butter: Choose your preferred vegan butter. If you’d rather, it can be replaced entirely or in part with vegetable shortening.

Step by step instructions

Here’s how to make this recipe at a glance. For complete ingredient amounts & instructions, keep scrolling to the recipe card below.

4-panel collage showing how to make rhubarb bars.

1. In a pot, combine the following:

Chopped rhubarb
Sugar
Cornstarch
Water
Vanilla extract

2. Stir frequently over a medium heat until thick like pie filling.

3. In a mixing bowl, combine the following:

Rolled oats
All-purpose flour
Sugar
Molasses
Non-dairy butter
Pistachios

Use a spoon and then your hands to make sure everything is evenly combined until there’s no dry flour left behind.

4. Pour about three-quarters of the oat mixture into a 9 x 13 baking dish. Lightly press it evenly across the dish.

Note: I use an ungreased glass baking dish. There’s enough non-dairy butter in the crisp that it comes out great. However, if you’d prefer to lightly oil your (metal or glass) baking dish, that’s fine too.

4-panel collage showing how to prepare rhubarb crisp bars.

5. Gently pour the rhubarb mixture across the oats. Use a spoon to evenly spread it.

6. Scatter the remaining oat mixture across the top of the rhubarb.

7. Put the baking dish into the oven, and bake 30 minutes, until golden brown.

8. You can eat the rhubarb bars while warm. But for easier slicing, allow it to cool somewhat before cutting into squares.

Make it your own

You can make this recipe your own by varying the ingredients.

Replace the cup of white sugar + molasses in the oats with a cup of brown sugar
Replace pistachios with an equal amount of chopped walnuts, pecans, almonds, or cashews
If you don’t like or can’t eat nuts, simply omit them
Replace non-dairy butter in part or in full with vegetable shortening
For an extra boost of flavor, add a dash of cinnamon to the oat topping

Serving ideas

Rhubarb crisp bar on plate with scoops of non-dairy ice cream.

These rhubarb bars are terrific on their own as a sweet treat. I especially like them with a cup of hot coffee or English breakfast tea.

They’re also great alongside a scoop or two of non-dairy vanilla ice cream.

Storage instructions

Gold fork being speared into oatmeal rhubarb bar.

To keep the oat topping crispy, wait until the bars have cooled before covering them.

The covered bars can be stored at room temperature on the counter for a day or two. After that, move them to the fridge. Over time, the crispy topping will start to soften. You can still enjoy them that way, or re-crisp them in the air fryer or oven.

Plan on eating the bars within about 3 or 4 days.

Rhubarb bars also freeze well. I like to wrap each bar individually in plastic wrap, and then put them all into a large freezer bag.

When you’re ready to eat them, you can pull out just as many bars as you need. Nosh on them right out of the freezer, or let them thaw in the refrigerator. Quickly warm them in the microwave, or re-crisp in the oven or air fryer.