First, let me just say… thank you. Thank you for being here, for clicking on this recipe, for continuing to make homemade desserts feel like love letters from the kitchen. If you’ve ever found yourself holding a bunch of rhubarb and wondering what could possibly elevate its tart charm, you’ve come to the right place. This Raspberry-Rhubarb Slab Pie is everything I adore about summer baking—bright, bold, and bursting with nostalgia. And the smell when this is in the oven? Absolutely dreamy.

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Why You’ll Love This Raspberry-Rhubarb Slab Pie

Let’s talk about what this recipe is. It’s an easy-to-share, easy-to-make twist on a traditional pie. It’s made in a sheet pan, which makes it perfect for serving a crowd (hello, backyard barbecue or Sunday brunch!). I promised you versatile, and here’s proof! This pie is sweet but not overly so, with a raspberry tang and that zingy rhubarb edge. The filling is silky, the crust golden and crisp, and together they deliver a bite that’s anything but boring!!

What does it taste like? Imagine the familiar comfort of Grandma’s rhubarb pie—just bigger, brighter, and with a ruby-red twist. The raspberries melt into the rhubarb, creating a jammy, luscious center that’s wrapped in a buttery, flaky lattice top. It’s both rustic and elegant, casual enough for a picnic, but pretty enough for a dinner party.

Benefits of Making a Slab Pie

Feeds a crowd: No more tiny wedges—this pie gives generous portions.
Easier than a round pie: No fluting or deep-dish drama. Just roll, fill, bake.

Great for summer events: Sturdy enough to travel, gorgeous on a potluck table.
Flexible filling: Don’t have raspberries? Swap in strawberries or cherries. More on that below!

Ingredients

2 pie crusts (homemade or store-bought)

2 ½ cups fresh rhubarb, chopped
2 cups fresh raspberries
1 ¼ cups granulated sugar

¼ cup cornstarch
1 tbsp lemon juice
½ tsp vanilla extract

1 egg, beaten (for egg wash)
Optional: coarse sugar for topping

Homemade Raspberry Rhubarb Slab Pie cooling on a baking sheet, filled with juicy raspberries and tart rhubarb

Tools You’ll Need

Rimmed baking sheet (10×15 inch works best)

Rolling pin
Mixing bowls
Whisk

Pastry brush
Knife or pizza cutter for lattice strips

Ingredient Substitutions & Additions

No raspberries? Use strawberries, blackberries, or even cherries.

Frozen fruit? Totally fine. Just thaw and drain excess liquid first.
Want it spicier? Add a pinch of cinnamon or a grating of fresh ginger.
Going gluten-free? Use a GF crust and sub in arrowroot for the cornstarch.

How to Make Raspberry-Rhubarb Slab Pie

Preheat oven to 400°F (200°C). Line your baking sheet with parchment or lightly grease it.
Roll out one pie crust to fit your sheet pan, with a slight overhang. Press it into the corners.
Make the filling: In a large bowl, combine rhubarb, raspberries, sugar, cornstarch, lemon juice, and vanilla. Stir gently to coat.

Add filling evenly over the bottom crust.
Create the lattice: Roll out the second crust and cut into strips. Lay them over the pie in a criss-cross pattern. (No stress if it’s not perfect—rustic is beautiful!)
Seal and brush: Tuck or trim the edges and brush the top with egg wash. Sprinkle with coarse sugar if desired.

Bake for 35–40 minutes, or until the crust is golden and the filling is bubbling.
Cool completely before slicing so the filling sets.

What to Serve with It

A scoop of vanilla bean ice cream (YES!)

Lightly sweetened whipped cream
A drizzle of raspberry coulis or lemon glaze
Fresh mint for garnish

Tips for Success

Let the pie cool fully before slicing—this helps it hold together.
Don’t skimp on cornstarch—it keeps your filling from turning runny.
For the best crust, keep your dough cold until baking time.

If the top browns too quickly, tent loosely with foil in the last 10 minutes.

How to Store It

Room temp: Store covered up to 2 days.
Fridge: Up to 5 days in an airtight container.

Freezer: Wrap tightly and freeze slices for up to 3 months. Thaw overnight in the fridge and reheat in a low oven.

General Info You’ll Want to Know

This pie is just as good chilled as it is warm. It travels well, slices beautifully, and even makes a charming breakfast the next day (with coffee, of course). It’s also a great base recipe to experiment with—think rhubarb-peach, blueberry-rhubarb, or even cranberry in the fall!

Frequently Asked Questions

Can I use store-bought pie crust?
Absolutely! This is meant to be easy and approachable.

Do I have to make a lattice top?
Not at all. You can lay the top crust flat and cut slits for steam—or go full creative with cut-outs or crumb topping.

Can I prep this ahead of time?
Yes! Make and chill it up to 1 day before baking. You can also freeze the unbaked assembled pie.

What if my filling is too runny?
Make sure you’re using enough thickener and letting the pie cool completely before cutting.

In Summary

This Raspberry-Rhubarb Slab Pie is your ticket to easy elegance. It’s juicy, just sweet enough, and practically screams summer on a plate. Whether you’re feeding a backyard crowd or just want a new twist on a classic, this one’s a keeper.

Want more peachy-keen desserts? Be sure to check out my Peach Crumble Bars, Peach-Almond Galette, and Grilled Peach Shortcake—all reader favorites!

Tried it? I’d love to see! Leave a review below or tag your bake on Pinterest so we can all drool over it together.

Nutritional Information (per serving, approx.)

Calories: 280
Fat: 12g
Carbohydrates: 41g

Sugar: 21g
Fiber: 3g
Protein: 3g

Is this going to be your new summer staple?