This mixed berry pie is a sweet combination of blueberries, blackberries, and strawberries topped with a buttery, crunchy oatmeal crumble topping.
Make this easy dessert any time for a delicious treat!

This post is sponsored by Seal the Seasons, but the content and opinions expressed here are my own.
The first time I ate this heavenly oatmeal crumble topping was topped on a Cranberry Apple Casserole that my cousin made.
It is a sweet and tart casserole with a gooey apple cranberry filling that is absolutely FANTASTIC!! I fell in love with it.
We make it for Thanksgiving and Christmas holidays.
When I decided to create this mixed berry pie, I wanted the same crunchy oatmeal topping topping that compliments the fruit so well, rather than the typical pie crust topping.
I was so pleased with the results.
The buttery crunch of the topping cuts some of the sweetness of the sweet and tart mixed berry filling, while the flaky pie crust ties all the flavors together.
This really is a marvelous marriage of flavors.
Mixed berry pie video
How to make a Mixed Berry Pie with Oatmeal Crumble Topping
Follow these easy steps to make mixed berry pie with oatmeal crumble topping.
- Completely thaw out your frozen mixed berries. Drain any excess liquid. (Photo 1)
- Preheat oven to 400 degrees.
- In a large mixing bowl, mix berries, sugar, cornstarch, lemon juice and vanilla. Toss until evenly coated. (Photo 2)
- Pour berry filling into a 9 inch pie crust. (Photo 3)
- Cut butter into slices.
- In a seperate mixing bowl, combine old-fashioned oats, brown sugar, cinnamon, all purpose flour, and butter slices. (Photo 4)
- Mix with a pastry blender until pea sized clumps form. (Photo 5) The Professional Dough Blender, Pastry Cutter Stainless Steel, Heavy Duty Pastry Blender with Blades by Zulay Kitchen
is a great pastry blender if you need one.
- Sprinkle oatmeal crumble topping evenly over the mixed berries until completely covered. (Photo 6)
- Bake for 30 minutes.
- Reduce the oven temperature to 350 and bake an additional 15-20 minutes.
- Cool for 2 hours at room temperature before serving.
Note: Resist the temptation to cut into this pie immediately. It is important not to skip cooling for 2 hours. Cooling it allows the filling to thicken.
Should you use a homemade pie crust to make this mixed berry pie?
I use a store bought prepared pie crust to keep this mixed berry pie recipe simple and easy to make.
However, if you want to make a pie shell from scratch, Sally's Baking Addiction has a wonderful tutorial on how to make one.
Can you use Frozen Fruit in Pies?
Pies are a great way to use frozen fruit! Frozen fruit are frozen at their ripest point.
They can be purchased year round regardless of the seasons at a much less price than the fresh fruit.
They require less work to work with because they are already cleaned and stemmed.
When baking with frozen fruit, you should allow 10 to 15 minutes of additional baking time unless you thaw out the fruit. In this recipe, I want you to thaw out your fruit to control the cooking results in the oven.
Note: I use Seal the Seasons frozen mixed berries in this mixed berry pie with oatmeal crumble topping recipe. Seal the Seasons works with small local farms. The small farms harvest their produce at the ripest point. Seal the Seasons freezes their produce and sells them at your local grocery store such as Harris Teeter, Food Lion, Lowes Foods, and Whole Food.
This allows consumers to purchase local farms produce year round. It also allows family farms to make a reliable stream of income.
Did you know?
Most fruit bought outside of the fresh seasons are from other foreign countries. Since 2000, approximately 21 percent of small family farms have had to close down. Seal the Seasons strives to give local family farmers economical opportunities to help them stay open for business.
Do you need to refrigerate leftover mixed berry pie?
You can keep this mixed berry pie out at room temperature for up to 2 days.
Cover it with foil or saran wrap while storing. It will keep an additional 3 days in the refrigerator.
For more Fruit Recipes, try:
- Caramel Apple Turnovers
- Ambrosia Fruit Salad
- Homemade Peach Salsa
- Strawberry Lemonade Punch
- Red, White, and Blue Sangria Sparklers
- Blender Strawberry and Mango Wine Slushy
When you make this mixed berry pie, tell me what you think in the comment section! I would love to hear back! My readers will too.
Also post your picture of your pie on Instagram or Facebook, and tag @aforkstale and @sealtheseasons with #aforkstale #sealtheseasons hashtags! I will share with my followers! xoxo!
Recipe
Mixed Berry Pie with Oatmeal Crumble Topping
Equipment
- pastry blender
Ingredients
- 6 cups frozen mixed berries (blueberries, blackberries, and strawberries I use Seal the Seasons
- 1 cup sugar
- ¼ cup cornstarch
- 2 tbs lemon juice
- 1 teaspoon vanilla extract
- 9 in deep dish pie crust
Oatmeal Crumble Topping
- 1 cup old-fashioned oats
- ¾ cup brown sugar
- ½ cup all purpose flour
- 1 teaspoon cinnamon
- 9 tbs salted butter
Instructions
- Completely thaw 6 cups frozen mixed berries. Drain any excess liquid.
- Preheat oven to 400 degrees.In a large mixing bowl, mix berries, 1 cup sugar, ¼ cup cornstarch, 2 tbs lemon juice and 1 teaspoon vanilla. Toss until evenly coated.
- Pour berry filling into a 9 inch pie crust. Pour berry mixture into a 9 inch deep dish pie crust.
Create the Oatmeal Crumble Topping
- Cut 9 tbs of salted butter into slices.
- In a seperate mixing bowl, combine 1 cup old-fashioned oats, ¾ cup brown sugar, 1 teaspoon cinnamon, ½ cup all purpose flour, and butter slices. Mix with a pastry blender until pea sized clumps form.
- Sprinkle oatmeal crumble topping evenly over the mixed berries until completely covered.
- Bake for 30 minutes.
- Reduce oven temperature to 350 and bake an additional 15-20 minutes.
- Cool for 2 hours at room temperature before serving.