Baking Desserts raspberry crumble bars oats make-ahead summer gluten-free optional

Raspberry Crumble Bars

Name: Raspberry Crumble Bars
Prep time: 25 min
Cook time: 37 min
Total time: 1 h 2 min
Yield: 8 servings
Cuisine: American
Ingredients: 1 cup all-purpose flour (or certified gluten free flour blend); 1 cup old-fashioned rolled oats (certified gluten free if necessary); 0.75 cup light brown sugar (loosely packed); 0.5 teaspoon baking powder; 1 pinch fine sea salt; 0.5 cup salted butter, melted; 2 cups fresh raspberries; 0.25 cup granulated sugar (adjust to taste); 1 tablespoon cornstarch; 1 tablespoon freshly squeezed lemon juice

Buttery oat crumble bars with a bright, jammy raspberry filling — a tender, shortbread-like oat base and crunchy crumble topping that surround a tart, set berry center. These easy, make-ahead bars bake in a single 8x8-inch pan and slice clean once fully cooled.

0.0(0 reviews)

Prep: 25m · Cook: 37m · Total62 mins

DifficultyEasy

Serves8

AuthorSara

Sara's note

"These bars balance a buttery, oat-laced crumble with a simple raspberry filling that bakes in the oven — no stovetop required. They’re terrific for summer gatherings or boxed lunches and keep well in the fridge for several days."

Raspberry Crumble Bars

Raspberry Crumble Bars live at the intersection of tender shortbread and rustic oat crumble — a buttery, slightly chewy base topped with a jammy, bright raspberry center and a crunchy, golden streusel. The contrast is what makes them addictive: the oats and brown sugar bring toasty depth, the raspberries add clean acidity and perfume, and the cornstarch gives the filling a glossy, set texture that slices clean once fully cooled. Because they bake in a single 8x8 pan and use pantry-forward ingredients, they’re a reliable, unfussy treat for day-to-day baking or a make-ahead dessert for casual entertaining.

What makes this version work is the two-stage bake: par-baking the base firms the shortbread so it won’t turn soggy under the fruit, while the remaining crumble bakes to a crisp without overbrowning. I use melted salted butter to ensure even distribution through the oat mixture and to create those large, buttery crumble clusters you want on top. These bars are ideal for lunchboxes, coffee hour, or a light finish to a weeknight meal — and they improve after a few hours or overnight in the refrigerator when the filling fully gels and the flavors marry.

Plan your timing

Enter your target meal time:

5:55 pm–6:05 pm→Preheat and prepare pan

6:05 pm–6:15 pm→Mix the oatmeal crumble

6:15 pm–6:25 pm→Press and par-bake the base

6:25 pm–6:35 pm→Prepare the raspberry filling

6:35 pm–6:45 pm→Assemble and top

6:45 pm–6:55 pm→Bake, cool, and slice

Ingredients

Yield

Instructions

Preheat and prepare pan

Preheat the oven to 350°F (175°C). Line an 8x8-inch (20x20 cm) baking pan with parchment paper, leaving an overhang on two sides to lift the bars out easily.

Mix the oatmeal crumble

In a large bowl, stir together the flour (or GF blend), rolled oats, light brown sugar, baking powder, and sea salt until evenly combined. Pour in the melted salted butter and mix with a spatula until the mixture forms coarse crumbs with some larger chunks for texture.

Press and par-bake the base

Press about half of the crumble mixture firmly and evenly into the bottom of the prepared pan to form a compact base. Use the bottom of a measuring cup or your fingers to smooth the surface. Bake for 12–15 minutes, or until the base is set and just beginning to turn golden.

Prepare the raspberry filling

While the base par-bakes, gently toss the raspberries with the granulated sugar, cornstarch, and lemon juice in a bowl until evenly coated. Let sit briefly so the sugar begins to draw juices from the berries.

Assemble and top

Spread the raspberry mixture in an even layer over the warm par-baked base. Crumble the remaining oat mixture over the top, leaving some larger pieces for a rustic texture, and press very lightly so the topping adheres but stays crumbly.

Bake, cool, and slice

Return the pan to the oven and bake 25–27 minutes, or until the topping is golden and the raspberry filling is bubbling in the center. If the edges brown too quickly, tent loosely with foil. Cool completely in the pan on a wire rack (at least 1½–2 hours) to let the filling set, then use the parchment overhang to lift out and slice into 8 bars.

Tips from the kitchen

Press base firmly

Compressing the bottom layer firmly into the pan creates a compact shortbread that holds together when sliced; use the bottom of a measuring cup for even pressure.

Par-bake base first

Baking the base 12–15 minutes before adding the filling prevents a soggy bottom by setting the dough so it doesn’t absorb excess berry juices.

Adjust cornstarch amount

If your raspberries are very juicy or frozen, increase cornstarch to 1½ tablespoons to ensure the filling sets firmly after cooling.

Cool completely before slicing

Let the pan cool 1½–2 hours (or refrigerate 2–4 hours) so the filling firms; for clean slices, chill briefly and cut with a hot, dry knife between warm water dips.

Protect edges from overbrowning

If the crumble is browning faster than the filling is bubbling, tent the pan loosely with foil for the final 10–12 minutes of baking.

Variations & substitutions

Mixed Berry Twist

Swap half the raspberries for blackberries or blueberries and add 1 teaspoon lemon zest to the filling for more complexity and a slightly sweeter profile.

Almond Oat Crumble

Replace 1/4 cup of the flour with finely ground almond flour and stir 1/3 cup chopped toasted almonds into the crumble for a nutty flavor and extra crunch.

Vegan Coconut Version

Use refined coconut oil (melted) in place of butter and a flax 'egg' (1 tbsp ground flax + 3 tbsp water) if you want a slightly firmer crumb—ensure your oats and flour are certified vegan.

Jam Shortcut

For speed, swap the fresh raspberries for about 1 to 1¼ cups of thick raspberry jam mixed with 1 teaspoon lemon juice and a pinch of cornstarch to mimic fresh fruit texture.

Storage & make-ahead

Stored in an airtight container, these bars keep in the refrigerator for up to 5 days; the chill helps the filling remain set. You can freeze whole or sliced bars for up to 3 months — wrap individual slices in plastic and foil. To serve, thaw in the refrigerator and bring to room temperature for 20–30 minutes, or warm briefly in a low oven if you prefer them slightly soft.

What to serve with it

Serve bars with a dollop of lightly sweetened whipped cream or a scoop of vanilla ice cream to balance the bright tartness. For brunch, pair with a strong coffee or a floral tea like Earl Grey; for an afternoon pick-me-up, they’re lovely with a glass of milk or a chilled rosé.

Frequently asked questions

Can I use frozen raspberries?

Yes — thaw and gently drain any excess water, then toss with the sugar, cornstarch, and lemon juice; you may need an extra 3–5 minutes of baking and consider increasing cornstarch to 1½ tablespoons to compensate for extra moisture.

Why does the filling stay runny?

Runny filling is usually from underbaking or insufficient thickener; make sure the filling is visibly bubbling in the center during baking and cool the bars completely (or refrigerate) so the cornstarch fully gels.

My bars fall apart when cut — how do I fix that?

Press the base more firmly before par-baking and ensure the base is fully set and golden; chilling the finished pan before slicing also helps the bars hold their shape.

Can I halve or double the recipe?

Halving works well in a smaller pan; doubling should be baked in a 9x13-inch pan but expect slightly longer bake times (monitor for bubbling filling and golden topping).

What can I use instead of cornstarch?

Arrowroot works as a 1:1 substitute and gives a clear finish; all-purpose flour can be used but requires a bit more (about 2–3 tablespoons) and yields a less glossy filling.

About the author

Sara See all recipes by Sara →

Ratings & Reviews

Did you make this recipe?

Be the first to share your experience.

Ingredients

8 servings

all-purpose flour (or certified gluten free flour blend)1 cup
old-fashioned rolled oats (certified gluten free if necessary)1 cup
light brown sugar (loosely packed)0.75 cup
baking powder0.5 teaspoon
fine sea salt1 pinch
salted butter, melted0.5 cup
fresh raspberries2 cups
granulated sugar (adjust to taste)0.25 cup
cornstarch1 tablespoon
freshly squeezed lemon juice1 tablespoon

Nutrition Facts

Per serving: about 110g

Calories318

Total Fat15g

Saturated Fat8.8g

Trans Fat0.6g

Polyunsaturated Fat3.6g

Monounsaturated Fat0.7g

Total Carbohydrates45.7g

Dietary Fiber0.9g

Total Sugars21.1g

Protein3.1g

Nutrition values are estimated from USDA ingredient data and may vary based on preparation, brands, and portion sizes. Values are provided for informational purposes only.

Keep Reading

Guides & articles for this recipe

All articles →

Tips & Techniques

Seasonal Flavor Framework

A practical guide to composing balanced late-summer plates by pairing charred proteins, smoky accents, bright quick pickles, fresh herbs, and crunchy textures. Includes short technique boxes (quick pickles, finishing oils, compound butters) and clear timing notes so readers can mix-and-match market produce into satisfying meals.

Guides

Late-Summer Sips Guide

An ingredient-first guide to 10–12 late-summer cocktails and mocktails that turn peaches, watermelon, tomatoes, herbs, and stone fruit into vibrant drinks. Covers shrubs, grilled and charred fruit, tea infusions, batch methods, low-ABV swaps, and pairing notes for backyard grills.

Guides

Trending Charred Fruit Finishes

A practical guide to finishing grilled late‑summer fruits—peaches, plums, pineapple, and citrus—using glazes, brûlée sugars, herb‑salt contrasts, cheese pairings, and boozy sauces. Includes step‑by‑step techniques, eight quick finish recipes, and pairing ideas for desserts, salads, and grill‑side cocktails you can make tonight.