Mixed Berry Slab Pie (Raspberry, Blackberry & Blueberry)

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Everything you love about berry pie, baked in a sheet pan! One mixed berry slab pie easily yields 18-24 slices, so it's perfect for sharing with friends.

You might also like our apple slab pie, blackberry pie, or strawberry rhubarb slab pie.

My mixed berry slab pie (sometimes called a Razzelberry pie) is absolutely delicious, the perfect combination of sweet and tart. It’s sturdy enough to pick up a slice by hand, though I prefer eating it with a fork. Slab pie is easier to serve than a regular pie and stays fresh for up to 3 days, making it great for leftovers. The best part? The pie crust doesn't get soggy...ever.

Why I Love This Recipe

Basic ingredients: My pie crust recipe is a keeper, a variation of my favorite pie crust recipe from Betty Crocker. It uses shortening, butter, and oil for the best texture and flavor.
The crust is forgiving: Not great at making pie crust? That's ok. Slab pie tastes delicious regardless, and because it's made with a combination of shortening, oil, and butter, it's a little easier to roll out than an all-butter pie crust. Do your best to roll it into a rectangular shape, but just know that once it's baked up, the golden top and bubbly filling will hide imperfections.
Stays fresh for several days: Mine have been kept for at least 3 days, making this a great dessert to make the night before you need it.
Serves a crowd. One slab pie will serve 18-24 people. I make my slab pies in a 10×15″ jelly roll pan. This is a great all-around size. It's smaller than the half-sheet baking pans that I typically use, but easier to work with when rolling out the dough. You can turn any pie recipe into a slab pie by doubling your favorite two-crust pie crust recipe and making about 1 ½ batches of pie filling. Make sure to follow my tips and tricks for achieving a perfectly baked crust (top and bottom)---very important!

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Why I Love This Recipe
🥧 5 TIPS FOR BAKING SLAB PIES
Ingredients
How to Make Mixed Berry Slab Pie
Mixed Berry Pie FAQs
More Berry Recipes To Make
Mixed Berry Slab Pie

Slice of mixed berry slab pie with ice cream on plate.

🥧 5 TIPS FOR BAKING SLAB PIES

Fruit pies, if not properly baked, can end up with an underbaked bottom crust or one that goes soggy after a few hours. This is because fruit fillings break down during baking and leak juice. Having a properly thickened filling (using flour) and making sure your crust is baked properly is key. This is especially important with slab pie because it has a large surface area.

Use Crust Dust: I first learned about the miracle of CRUST DUST (see image above) from King Arthur Flour. It's super easy to make, too! Crust dust is a 1:1 ratio of all-purpose flour and sugar. You simply mix the two ingredients together, then sprinkle it over the bottom crust in a THIN layer before adding the pie filling. As the pie bakes, the flour and sugar create a barrier, preventing the juices from soaking into the crust. It really works, too, and once baked, you won't even know it's there.
Bake In Bottom ⅓ of Oven: Baking the pie lower in the oven (I bake on the second to bottom rack position) helps the bottom crust to bake evenly.
Use a Baking Stone: I swear by baking my pies on top of a preheated baking stone (pizza stone). If you don't have one that's ok! The first two tips will still yield a delicious crust. The baking stone just helps center the heat evenly for the bottom crust.
Use a Metal Pan: metal pie pans work better than glass for a golden bottom crust.
Don't Worry About Overbaking Your Pie: yep, that's what I said. It's better to slightly overbake the crust vs. underbake. I bake my slab pies for 30 minutes, then loosely cover with foil for another 20-25 minutes. Covering the pie for the last half of the baking process will help the top not get too brown.

Remember: if the filling isn't bubbling up and almost coming out of the pie, it's not done!

Ingredients

Stick of butter, bowls of shortening, flour, sugar and salt, bottles of oil and milk, lemon juice and fresh berries.

Pie Crust

Flour
Salt
Butter, Shortening, and Oil: You'll notice that the pie crust calls for all 3 of these fats. Each one has its purpose and helps create a delicious and flaky pie crust that rolls out easily and does not need to chill. I highly recommend NOT substituting any of these ingredients.
Milk or buttermilk: You can use buttermilk or a combination of milk and lemon juice. I don't always have buttermilk on hand, so I use the milk and lemon juice hack.
Sugar: The pie is brushed with an egg wash, then sprinkled with sugar before baking, resulting in a golden, sweet crust.

Glass bowl of blackberries, blueberries and raspberries.

Mixed Berry Filling

Raspberries, blackberries, and blueberries. I like using equal amounts of each, but you can cater the portions however you'd like. You need 36 ounces of whatever berry combination you'd like.
Sugar: Adds sweetness to balance out the tart flavors of the blackberries and raspberries.
Flour and cornstarch: These work together to thicken the filling perfectly.
Lemon juice: Brightens the flavors of the berries in the pie filling.

See the recipe card for full information on ingredients and quantities.

How to Make Mixed Berry Slab Pie

Hand holding ball of pie dough wrapped in plastic.

Step 1: Mix flour and salt in a large bowl. Cut in shortening using a pastry cutter. Cut in butter until the particles are the size of small peas. Combine the milk and lemon juice in a small bowl. Add oil and milk/lemon mixture to the flour mixture and stir until a soft dough forms. Divide dough into 2 pieces, wrap in plastic and chill for 30 minutes.

Pie dough rolled out onto jelly roll pan.

Step 2: Roll the pie crust on a lightly floured surface. Keep rolling until it is a 13x18" rustic-looking rectangle. It won't be exact, and that's ok. Place the rectangle into a 10x15" jelly roll pan, allowing the excess to hang over the edge of the pan.

Step 3: Sprinkle crust dust over the pie crust bottom.

Step 4: Combine filling ingredients in a large mixing bowl and stir to coat the fruit evenly. Pour filling into the pie crust and spread evenly.

Hands rolling and tucking pie crust into the pan.

Step 5: Roll the second crust out into a rustic-looking 13x18" rectangle. Place on top of the pie. Fold the edges of the top and bottom crust back and tuck them into the pan. Use your fingers to pinch and crimp the edges of the pie (or use a fork to crimp).

Step 6: Cut slits into the top of the pie to allow steam to vent while baking. Brush the crust lightly with egg wash, then sprinkle with sugar.

Step 7: Bake slab pie for 30 minutes. Cover/tent loosely with foil and bake for an additional 20-25 minutes. The top should be GOLDEN and the filling should be bubbling.

Pie is best served after it's had a chance to cool for at least 2 hours. Wrap the cooled slab pie in plastic and store at room temperature for 2-3 days.

Mixed Berry Pie FAQs

How do I store berry slab pie?

Store leftover pie in the pan, covered with plastic wrap, to keep fresh for up to 3 days.

What pans work best for slab pies?

I only bake on light-colored baking sheets. If you bake on dark sheets, you may need to adjust the baking time. A jelly roll pan is the perfect size for making a slab pie.

Can I use frozen berries to make mixed berry pie?

You can use fresh or frozen berries to make a mixed berry slab pie. DO NOT thaw the berries prior to baking; use frozen.

Can I omit shortening in this recipe?

Anytime I use shortening in a recipe, I am asked if you can use butter instead. I prefer using a combination of butter and shortening for the best flavor and texture. The shortening makes the dough easier to roll out because it doesn't warm up when I work it with my hands, but you can absolutely use all butter.