# Strawberry Rhubarb Crumble Bar > Bright, tangy strawberry-rhubarb filling is sandwiched between a buttery oat-crumble base and crunchy oat topping for an irresistible bar. These bake in a single 8x8 pan and are perfect for spring gatherings, potlucks, or an easy make-ahead dessert. Canonical URL: https://www.topshelf.recipes/recipes/strawberry-rhubarb-crumble-bar ## Author Sara https://www.topshelf.recipes/chef/sara-woods Published: June 29, 2026 Last Updated: September 28, 2026 ## About This Recipe Bright, tangy strawberry and rhubarb meet a satisfyingly buttery oat crumble in these single-pan bars—an easy way to capture spring flavors without fuss. The dual oat layers are what make this version sing: old‑fashioned oats in the base provide chew and structure so the bars hold together, while reserving a portion of the crumble for the topping creates textural contrast and lets the filling bubble up through golden pockets. A short par-bake firms the crust so the fruit juices don’t turn it into mush, and a judicious amount of cornstarch plus a squeeze of lemon keeps the filling glossy and balanced against the rhubarb’s natural tartness. This recipe is written for home bakers who want an impressive but low-stress dessert for potlucks, picnics, or a weeknight treat—make it the day before to get clean slices and deeper flavor. Because the recipe uses simple pantry items and minimal hands-on time, it’s forgiving to small substitutions (gluten‑free oats, a touch of ginger, or coconut oil for a vegan spin). Slice them cold for tidy squares, or warm a piece and serve with vanilla ice cream for a softer, more decadent presentation. ## Recipe Information - Prep Time: 20 minutes - Cook Time: 35 minutes - Total Time: 55 minutes - Servings: 8 - Difficulty: Easy - Category: Baking ## Ingredients ### Make the oat-crumble base and reserve topping - 1 cup all-purpose flour - 1 cup old-fashioned rolled oats - 3/4 cup light brown sugar (loosely packed) - 1 pinch fine sea salt - 1/2 cup salted butter, melted ### Prepare the strawberry-rhubarb filling - 2 cups fresh strawberries, hulled and quartered - 1 1/2 cups fresh rhubarb, trimmed and chopped - 1/3 cup granulated sugar (adjust to taste) - 1 1/2 tablespoons cornstarch - 1 tablespoon fresh lemon juice ## Instructions ### 1. Make the oat-crumble base and reserve topping Preheat oven to 350°F (175°C) and line an 8x8-inch square pan with parchment, leaving an overhang. In a medium bowl combine flour, rolled oats, light brown sugar, and a pinch of salt; stir to mix. Pour in the melted butter and stir until the mixture holds together when pressed; set aside about 1 to 1¼ cups of this mixture for the topping, then press the remaining mixture firmly and evenly into the prepared pan. Par-bake the crust for 10–12 minutes, until just set and beginning to turn golden. ### 2. Prepare the strawberry-rhubarb filling While the crust par-bakes, toss the strawberries and rhubarb with granulated sugar, cornstarch, and lemon juice in a bowl until evenly coated. Let the fruit sit 5–10 minutes to macerate; if the fruit is very juicy, you can increase cornstarch by 1 teaspoon. Taste and add a little more sugar if desired—the rhubarb can be quite tart. ### 3. Assemble the bars Spread the macerated strawberry-rhubarb mixture evenly over the warm, par-baked crust, gently pressing any large pieces so the layer is compact. If there is excess liquid at the bottom of the bowl, spoon mostly the fruit and thickened juices into the pan to avoid a soggy crust. ### 4. Top with reserved crumble Evenly sprinkle the reserved oat-crumble mixture over the fruit layer, breaking up any large clumps so the topping is slightly lumpy and allows the filling to bubble through. Lightly press a few spots so the topping contacts the filling but remains textured. ### 5. Bake until bubbling and golden Return the pan to the oven and bake 22–28 minutes, until the fruit filling is bubbling in the center and the topping is golden brown. If the topping browns too quickly, tent loosely with foil for the last 5–10 minutes. ### 6. Cool, chill, and slice Allow the bars to cool on a wire rack until they reach room temperature, then chill in the refrigerator at least 2 hours (overnight is best) to fully set the filling. Use the parchment overhang to lift the slab from the pan and slice into 8 bars with a sharp knife, wiping the knife between cuts for clean edges. ## Nutrition Estimated nutrition per serving (1 serving): - Calories: 327 kcal - Protein: 3.7 g - Carbohydrates: 51.7 g - Fat: 12.5 g - Saturated Fat: 7.4 g - Fiber: 2.7 g - Sugar: 28.9 g - Added Sugars: 26.6 g - Cholesterol: 30.4 mg - Sodium: 122.8 mg - Potassium: 210.2 mg - Calcium: 52.7 mg - Iron: 1.6 mg - Vitamin D: 0.2 mcg ## Tips ### Par‑bake the crust Par‑baking for 10–12 minutes sets the base so the fruit layer won’t make it soggy; press the crust firmly and evenly into the pan for a stable bar that slices cleanly. ### Reserve the topping Set aside 1 to 1¼ cups of the crumble before pressing the base; this keeps the topping lighter and allows the fruit to peek through when it bakes. ### Adjust cornstarch carefully If your fruit is very juicy, add an extra teaspoon of cornstarch to prevent a runny filling, but avoid over‑thickening which can make the filling gummy. ### Macerate briefly Let the strawberries and rhubarb sit with sugar and lemon for 5–10 minutes to draw out juices and dissolve the sugar so the cornstarch can thicken evenly. ### Chill before slicing Refrigerate at least 2 hours (overnight is best) so the filling fully sets; use a hot, sharp knife and wipe between cuts for neat squares. ## Variations and Substitutions ### Gluten‑free swap Use certified gluten‑free rolled oats and replace the all‑purpose flour with an equal amount of almond flour or a 1:1 gluten‑free baking flour for a similar texture. ### Vegan version Substitute melted coconut oil or vegan butter for the butter and use brown sugar; chilling slightly longer helps the filling set since coconut oil is softer at room temperature. ### Spice & flavor twist Stir 1 teaspoon of grated fresh ginger or ½ teaspoon ground cardamom into the filling for warmth, or add 1 teaspoon vanilla extract to the fruit for a rounder flavor. ### Other fruit combinations Swap strawberries and rhubarb for equal parts raspberries and rhubarb, or peaches and rhubarb (use slightly more cornstarch with very juicy peaches) for seasonal variations. ## Notes These bars balance bright, tart rhubarb with sweet strawberries and a buttery oat crumble—great warmed with a scoop of vanilla ice cream or chilled and packed for a picnic. Home bakers will love how reliably the filling sets after chilling, making clean slices every time. ### Storage and Make-Ahead Store cooled bars in an airtight container in the refrigerator for up to 4–5 days; chilling improves sliceability and flavor. For longer storage, wrap the slab tightly in plastic and foil and freeze for up to 2 months, thawing overnight in the fridge. Reheat individual portions briefly in a 300°F oven for 8–12 minutes to revive the topping, or microwave for 20–30 seconds for a warmed serving (the crust may soften). ### Serving Suggestions Serve chilled squares with a dollop of slightly tangy crème fraîche, whipped cream, or a scoop of vanilla ice cream that contrasts the tart rhubarb. Pair with a light tea, an americano, or a sparkling rosé for a springtime gathering, and consider a dusting of powdered sugar or a few fresh sliced strawberries on top for a pretty finish. ## Frequently Asked Questions ### Can I use frozen strawberries and rhubarb? Yes—use frozen fruit straight from the freezer and increase cornstarch by about 1–2 teaspoons because frozen fruit releases more water as it thaws and bakes; no need to thaw first. ### Why is my crust soggy on the bottom? A soggy bottom usually means the crust was under‑par‑baked or the fruit layer had excess liquid; press the base firmly, par‑bake until just golden, and spoon mostly fruit (not excess juices) into the pan. ### How can I tell when the filling is done? Look for the filling to be actively bubbling in the center and the topping to be golden brown; bubbling indicates the cornstarch has been activated and the filling is thickening. ### Can I make these ahead of time? Absolutely—these are better after chilling overnight, which firms the filling and makes slicing cleaner; store refrigerated and bring to room temperature or gently rewarm before serving if desired. ### Can I replace cornstarch with something else? You can use an equal amount of arrowroot powder for a clearer, glossy finish, or 1½ times the amount of tapioca starch; avoid flour, which can leave a pasty texture. ## Related Recipes and Guides - [Cloud Bread Sandwiches](https://www.topshelf.recipes/recipes/cloud-bread-sandwiches) - [Honey Mustard Chicken Nuggets](https://www.topshelf.recipes/recipes/honey-mustard-chicken-nuggets-baked) - [Cheddar Jalapeño Corn Muffins](https://www.topshelf.recipes/recipes/cheddar-jalapeno-corn-muffins) - [Basque Burnt Cheesecake](https://www.topshelf.recipes/recipes/basque-burnt-cheesecake-salted-caramel) - [30-Minute Sticky Baked Honey Garlic Chicken Thighs with Crisp Edges](https://www.topshelf.recipes/recipes/30-minute-sticky-baked-honey-garlic-chicken-thighs-crisp-edges) - [Lemon Butter Salmon](https://www.topshelf.recipes/recipes/lemon-butter-salmon) - [Baking Soda and Tenderized Beef](https://www.topshelf.recipes/articles/baking-soda-and-meat) - [Gluten-Free Weeknight Grilling Plan](https://www.topshelf.recipes/articles/gluten-free-weeknight-grilling-plan) - [Low-Fat Grill Swaps for Big Flavor](https://www.topshelf.recipes/articles/low-fat-grill-swaps-big-flavor)