Delicious fruit crisp in square form! These strawberry rhubarb squares feature a homemade strawberry rhubarb filling with an oatmeal and shortbread base and crumble topping.

strawberry rhubarb crumble squares on parchment

These strawberry rhubarb squares start with an easy, homemade strawberry rhubarb filling. Strawberry rhubarb is one of my favourite fruit combinations, as it’s hard to beat that sweet/tart thing. Add to that an oat crumble, that acts as both the base of these squares and the crumble topping. Couldn’t be easier!

I’ve baked these up in an 8×8-inch pan, but the recipe easily doubles to feed a crowd, so they are perfect to take to a Summer picnic or BBQ. Enjoy out of hand, on a plate with a fork or warm slightly and serve with a small scoop of vanilla ice cream for a dessert.

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Ingredients and substitutions

A few notes about the key ingredients …

Rhubarb: You can start with either fresh or frozen diced rhubarb here. If you don’t have or prefer not to use rhubarb, you can use all strawberries (3 cups total). For all strawberries, you probably want to reduce the added sugar to about 1/2 cup, as it will be sweeter to start with.

Strawberries: Likewise, start with either fresh or frozen strawberries. Be sure to roughly chop before measuring.

Cornstarch: Also known as cornflour.

Lemon Juice: Lemon juice plays an important role in jam making, but we’re not making a classic jam here, so it’s not a deal-breaker if you don’t have any on hand to add. Simply omit.

Rolled Oats: This recipe calls for the large flake, old-fashioned rolled oats. I have not tested this recipe with quick-cooking oats.

Whole Wheat Flour: adds a nice, nutty flavour, but can be replaced with the same amount of all-purpose flour.

Salt: If you will be using salted butter instead of unsalted here, reduce the amount of additional salt you add to just a pinch.

Butter: The recipe specifies unsalted butter. If you only have salted butter, you can use it, but reduce the amount of additional salt you add to just a pinch.

Recipe tips!

  • Be sure to line your baking pan with parchment paper, leaving an overhang that allows you to grab and lift the squares out of the pan.
  • I like to refrigerate the squares for a bit before cutting. It just makes them easier to cut, for neater squares.
  • These squares keep well stored covered, at room temperature for several days, though the crumble does tend to soften somewhat over time. Don’t hesitate to make them ahead.
  • These squares can be frozen as well.
strawberry rhubarb squares cut on parchment

Top Tip!

Feeding a crowd? Double the recipe and bake up in a 9×13-inch pan instead.

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Get the Recipe: Strawberry Rhubarb Squares

Easy homemade strawberry rhubarb squares with a homemade strawberry rhubarb filling, between an oatmeal crumb base and topping.
4.91 stars from 10 ratings
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Prep Time: 15 minutes
Cook Time: 30 minutes
Total Time: 45 minutes
Yield: 12 squares

Ingredients

Filling:

  • 1 1/2 cups rhubarb, diced, fresh or frozen
  • 1 1/2 cups strawberries, fresh or frozen, diced
  • 1 Tablespoon lemon juice
  • 3/4 cup white sugar
  • 3 Tablespoon cornstarch
  • 1 teaspoon vanilla, or vanilla bean paste

Base/Topping:

  • 1 1/2 cups large flake,old-fashioned rolled oats
  • 1 1/4 cups all-purpose flour, spooned and levelled
  • 6 Tablespoons whole wheat flour
  • 3/4 cups light brown sugar, packed
  • 1 teaspoon baking powder
  • 1/2 teaspoon coarse kosher salt, or 1/4 tsp fine salt
  • 1/2 teaspoon ground cinnamon
  • 3/4 cup unsalted butter, melted

Instructions
 

  • In a medium saucepan, stir together the rhubarb, strawberries, lemon juice, white sugar and cornstarch. Heat over medium heat on the stove-top, stirring regularly. When the fruit softens sufficiently, use a potato masher to break it up into smaller pieces. Continue cooking until mixture comes to a boil and thickens, then remove from heat. Stir in vanilla. Allow mixture to cool to lukewarm before proceeding (or can be made ahead and refrigerated. Bring back to room temperature before proceeding).
  • Heat oven to 350F degrees (not fan-assisted) and line an 8 x 8-inch pan with parchment paper with overhang on all sides.
  • In a large bowl, combine oats, flour, whole wheat flour, brown sugar, baking powder, salt and cinnamon. Add melted butter and stir until the mixture forms streusel-like crumbs.
  • Press 2/3 of the crumb mixture into an even layer at the bottom of the prepared pan. Spread the cooled strawberry rhubarb filling in an even layer over the crust, then sprinkle the remaining crumb mixture evenly over the top of jam.
  • Bake until jam bubbles at edges and streusel is lightly browned, 30 to 35 minutes. Cool completely before slicing into 12 pieces. (*I like to cool to room temperature and then refrigerate a bit before slicing. It just makes for a neater slicing if you'd like to serve it as neat squares).

Notes

Be sure to read the notes above this Recipe Card, where I share some valuable tips, options, substitutions and variations for this recipe!
Cuisine: American, Canadian
Course: Dessert
Author: Jennifer Maloney
Serving: 1serving, Calories: 318kcal, Carbohydrates: 49g, Protein: 3g, Fat: 12g, Saturated Fat: 7g, Cholesterol: 30mg, Sodium: 104mg, Potassium: 156mg, Fiber: 2g, Sugar: 27g, Vitamin A: 370IU, Vitamin C: 12.3mg, Calcium: 40mg, Iron: 1.4mg
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