Preheat your oven: First, set that oven to 350°F (175°C). You want it nice and warm for the magic that’s about to happen!
Prepare the pan: Grab an 8x8 inch baking dish (or similar) and grease it well or line it with parchment paper. We want that Berry Buckle to come out without a fuss!
Mix the dry ingredients: In a big bowl, combine the flour, granulated sugar, baking powder, and salt. Give it a good whisk so everything's mixed evenly.
Mix the wet ingredients: Now, in another bowl, whisk together the milk, vegetable oil, and vanilla extract. Once that’s combined, you're ready to blend wet and dry!
Combine wet and dry mixtures: Pour the wet mixture into the dry ingredients and stir gently until just combined. Don’t overmix; it’s all about keeping it fluffy and tender!
Add the surprise ingredient: Time for the berries! Gently fold in the mixed berries—you want to keep them whole and juicy, not smashed.
Bake it: Pour the mixture into your prepared baking dish, spreading it out evenly. It’s like a canvas now! Pop it in the oven for about 30 minutes.
Make the crumb topping: While it’s baking, let’s whip up the crumb topping: In a bowl, mix old-fashioned oats, brown sugar, cinnamon, and softened butter until crumbly. It should look like little pebbles of deliciousness.
Add the crumb topping: Once the Berry Buckle has baked for about 30 minutes, carefully sprinkle the crumb topping over the top and return it to the oven for another 10 minutes until golden brown.
Cool down and enjoy: Take it out of the oven and let it cool for a bit—if you can resist! Slice it up, serve warm, and enjoy your beautiful creation.