Make this Mixed Berry Crumble with Frozen Berries baked in a cast iron skillet for the perfect golden, buttery topping. No thawing needed.. an easy, cozy dessert with blueberries and raspberries.

Mixed Berry Crumble with Frozen Berries (Cast Iron Skillet Cake with Blueberries & Raspberries)

Have a bag of frozen berries sitting in your freezer? This Mixed Berry Crumble with Frozen Berries is the kind of dessert that turns something simple into something special.

It’s baked in a cast iron skillet, layered with juicy blueberries and raspberries, and finished with a buttery lemon crumble topping that bakes up golden, crisp, and absolutely irresistible.

But hey.. no cast iron skillet laying around? No worries. A 9×13 or 9×9 baking dish will do the job just fine.. just expect a slightly different bake time. Same delicious outcome, no fancy equipment required.

Best part? No thawing required. Just grab your frozen berries, mix everything together, and let the oven do the work.

This is one of those cozy, rustic desserts that feels like it came from a bakery.. but it’s made right in your own kitchen.

If you love cozy crumble and crisp desserts like this, you might also like my Maple Coffee Cake or this easy Triple Berry Crisp.

Slice of warm blueberry raspberry skillet cake with crumble topping showing soft cake layers and juicy berries inside.

Why You’ll Love This Recipe

Uses frozen blueberries and raspberries
No thawing required
Baked in a cast iron skillet for perfect edges
Bright lemon flavor in both cake and crumble
Soft, moist cake with juicy berries throughout
Buttery crumble topping baked right on top
Perfect for dessert, brunch, or holidays
It’s completely acceptable to stand at the stove with a fork eating this straight from the skillet at midnight. No judgment here.

Why I Use a Cast Iron Skillet for This Recipe

This dessert is baked in a 12-inch cast iron skillet, and it makes all the difference.

Cast iron holds heat evenly and creates those golden, slightly crisp edges that you just can’t get from a regular baking dish. It also goes straight from oven to table, which makes this feel a little rustic and special without any extra effort.

If you’ve got a cast iron skillet sitting in your cabinet and you’re not quite sure what to do with it, this is your sign to start baking in it.

Just make sure to butter the skillet generously on the bottom and sides before adding the batter. This step is important.. it keeps everything from sticking and helps the edges bake beautifully.

Ingredients for Mixed Berry Crumble

Crumble Topping

1 cup all-purpose flour
¾ cup packed brown sugar
Zest of 1 lemon
½ cup softened butter

Cake Batter

2¼ cups all-purpose flour
2 tsp baking powder
½ tsp salt
1 cup granulated sugar
Zest of 2 large lemons
½ cup softened butter
¼ cup vegetable oil
1 egg
½ cup sour cream
¼ cup buttermilk
2 tbsp lemon juice
1 tsp vanilla extract
1 tsp lemon extract (optional)
1 cup frozen blueberries
1 cup frozen raspberries

How to Make Mixed Berry Crumble with Frozen Berries

Step 1: Prep the Skillet

Preheat oven to 350°F.
Generously butter a 12-inch cast iron skillet, making sure the bottom and sides are fully coated.

Step 2: Make the Crumble

In a bowl, mix flour, brown sugar, and lemon zest.
Cut in softened butter until crumbly. Set aside.

Step 3: Make the Cake Batter

In a bowl, whisk flour, baking powder, and salt.
In a separate bowl, cream butter and sugar until light and fluffy.

Add:

egg
sour cream
buttermilk
vegetable oil
lemon juice
vanilla extract
lemon extract (optional)
lemon zest

Mix until smooth.
Slowly add dry ingredients until just combined.

Lemon berry cake batter being mixed in a bowl with flour, sugar, sour cream, and lemon zest.

Step 4: Fold in Berries

Gently fold in frozen blueberries and raspberries.
Do NOT thaw the berries.

Frozen blueberries and raspberries being gently folded into lemon cake batter for berry skillet cake.

Step 5: Assemble

Pour batter into prepared skillet.
Sprinkle crumble topping evenly over the top.

Buttery lemon crumble topping being sprinkled evenly over berry cake batter in skillet.

Step 6: Bake

Bake at 350°F for 45 minutes in a 12-inch cast iron skillet.
The top should be golden brown and a toothpick inserted into the cake layer should come out with a few moist crumbs.

Golden baked lemon berry skillet cake with blueberry and raspberry filling topped with a buttery crumble crust in a cast iron skillet.

Step 7: Cool

Let rest for at least 20 minutes before slicing. This helps the cake set and the berries thicken.

Tips No One Tells You

Do not thaw frozen berries or the batter will turn watery
Blueberries hold shape better than raspberries when baked
Toss berries lightly in flour if you want less sinking
Skillet must be heavily buttered or the cake will stick
Crumble should look like damp sand, not paste
Lemon zest in both layers brightens the entire dessert
Overmixing the batter makes the cake dense
The cake continues setting as it cools
Always test doneness in the cake area, not berry pockets
A scoop of vanilla ice cream melts perfectly into warm slices

How to Keep Berry Crumble from Getting Watery

Use frozen berries straight from the freezer
Do not thaw before baking
Bake until the center is bubbling
Let the cake rest before slicing
Don’t underbake.. this is the #1 issue

Berry Bake Times by Pan Size

12-inch cast iron skillet (recommended)

350°F for 45 minutes
Even bake, golden edges, rustic finish

10-inch cast iron skillet

350°F for 50–60 minutes
Thicker batter layer, slightly longer bake time

9×13 baking dish

350°F for 40–50 minutes
Faster bake, softer edges

9×9 baking dish

350°F for 50–60 minutes
Thick, more cake-like center

Individual ramekins

350°F for 25–30 minutes
Great for single servings

How to Know It’s Done

Top is golden and set
Crumble is crisp and lightly browned
Cake springs back when touched
Toothpick comes out mostly clean (moist crumbs OK)

Optional Lemon Glaze (Breakfast or Dessert Upgrade)

This berry skillet cake isn’t just dessert.. it’s also incredible the next morning with coffee.

If you want to lean into that breakfast vibe, add a simple lemon glaze on top once the cake has mostly cooled to the touch.

1 cup powdered sugar, sifted
2–3 tablespoons fresh lemon juice
Pinch of salt

Whisk everything together until smooth and pourable. If it’s too thick, add a tiny splash more lemon juice. If it’s too thin, add a bit more powdered sugar.

Drizzle the glaze over the slightly cooled cake so it melts into the top without disappearing completely. It adds a bright, sweet-tart finish that takes the whole skillet cake up another level.

Variations and Substitutions

Mixed Berry Peach Crumble: add frozen peaches
Blueberry Crumble: use only blueberries
Blackberry Crumble: swap berries for blackberries
Strawberry Crumble: use frozen strawberries only
Lemon Berry Crumble: add extra lemon zest
Almond Berry Crumble: add sliced almonds to topping
Pecan Berry Crumble: add chopped pecans
Gluten-Free: use GF flour + certified GF oats
Dairy-Free: use vegan butter

How to Store Leftovers

Cover and store at room temperature for 1 day or refrigerate for up to 4 days. Reheat before serving for best texture.

Can You Freeze It?

Yes. Freeze baked slices tightly wrapped for up to 2 months. Thaw and warm before serving.

What to Serve with Mixed Berry Crumble

Vanilla ice cream
Whipped cream
Vanilla yogurt
Mascarpone
Warm heavy cream
Lemon drizzle

Frequently Asked Questions

Can I use frozen berries instead of fresh?

Yes. Frozen berries work perfectly and are ideal for this recipe.

Do I need to thaw frozen berries first?

No. Use them straight from the freezer.

Why did my cake turn watery?

This usually happens if berries were thawed or the cake was underbaked.

Can I make this ahead of time?

Yes. Bake, cool, and reheat before serving.

Can I use a different pan?

Yes. Adjust baking time based on pan size as listed above.

What Is the Difference Between a Crisp and a Crumble?

A crisp and a crumble are very similar baked fruit desserts, but the main difference is the topping.

A crisp typically includes oats in the topping, which bake up lighter and crispier, giving it more texture and crunch.

A crumble is usually made with flour, sugar, and butter, creating a softer, more streusel-like topping that bakes into rich, buttery crumbs.

That said, the lines have blurred over time, and many modern recipes (including this one) combine both styles. So whether you call it a crisp or a crumble, you’re really just describing a warm, baked fruit dessert with a buttery topping and juicy filling underneath.

If you’re more into the oat-heavy, crunchy topping style of a crisp, you’ll love my Apple Crisp or this tart and cozy Cranberry Crisp.. it’s the same cozy baked fruit idea with a little extra crunch in every bite.

What to Do with Frozen Berries

If you’ve got frozen berries in your freezer, this is one of the easiest and best ways to use them up. Instead of letting them sit unused, turn them into a warm, bakery-style dessert with almost no effort.

Final thoughts

At the end of the day, this is one of those recipes that proves simple ingredients can still do big things. Frozen berries, a little lemon, and a cast iron skillet come together to make something warm, cozy, and honestly a little hard to stop eating once it hits the table. Keep a bag of berries in the freezer and this dessert is never more than a few steps away.

Xoxo, Heather 💋