Easy Blueberry Bars with Oats
Layered with a shortbread-type crust, these blueberry crumb bars are packed with hints of cinnamon and lemon zest. Baked to golden perfection, every bite of these sweet squares will put a berry big smile on your face— get it? How long it takes: 20 minutes prep time and 50 minutes for cooking time. Equipment you’ll need: A saucepan, large bowl, pastry cutter, and glass baking dish. Servings: 20 servings, depending on how large you slice the bars. Made with fresh or frozen blueberries, the combination of a rich and crispy top with a soft interior is simply delightful. Plus, the homemade filling adds just the right amount of fruity tang to balance the flavors. They’ll remind you of a fruit crisp, like blueberry apple crisp, but in an easy-to-eat bar form. With a buttery oat topping, you might find yourself packing a couple (if not all) of these crumb bars for work. There’s no way you’ll be able to resist their crust and purple, jammy goodness— and neither will your coworkers, so keep an eye on your lunch bag!
Why You’ll Love These Bars
Their crumbly topping is enough to make anyone fall in love, but here are several other reasons to make them:
Year-round. This recipe is freezer-friendly and can also be made using frozen blueberries, meaning you can enjoy it any time of the year. Great for on-the-go. Pack them in little bags or containers and bring them with you for a sweet snack throughout the day. Flexible. You can easily use your favorite kind of berry in this recipe like raspberries, strawberries, or blackberries. You can use fresh or frozen berries, or even use a mix of them.
Ingredient Notes
With some blueberries and a couple of pantry staples, you’re all set to make these blueberry crumb bars. Check the recipe card at the bottom of the post for exact ingredient amounts.
For the Filling
Sugar – White granulated sugar is best for the filling. If you’re in a pinch, you can use brown sugar. Cornstarch – Cornstarch is used to thicken the fruit filling. Blueberries – I used fresh blueberries but you could also use frozen blueberries. No need to thaw them! Fresh lemon juice – The juice from 2 lemons should be about right. Lemon zest – Feel free to leave it out, but if you’re already using lemons, why skip it?
For the Bars
Quick oats – Avoid rolled oats because they’ll change the texture of the bars and they’ll be more likely to fall apart. All-purpose flour – Please don’t use any flour alternatives. Light brown sugar – Dark brown sugar is a good substitute. Don’t use granulated sugar for this. Ground cinnamon – Cinnamon gives the crust a nice, warm taste. Salt – A pinch of salt balances out the sweetness. Unsalted butter – Salted butter is also okay. If you use it, omit the salt in the recipe.
Can I Use Frozen Berries?
Yes! Throw them into the saucepan straight out of the freezer. They’ll cook and soften in the pot as you make the mixture. Don’t worry if they release lots of moisture at first, just cook the filling until it reduces and has slightly thickened.
How to Make Blueberry Crumb Bars
All you need to do to set these golden bars on your counter is make the filling, layer the bars, and bake. It’s easy!
Prepare the oven. Preheat oven to 325°F. If you’re not sure your oven is well calibrated, use a small oven thermometer to make sure it’s at the right temperature. Spray a 9 × 13-inch baking pan or dish with nonstick cooking spray.
Make the filling. Mix the sugar and cornstarch in a large saucepan. Add the blueberries, lemon juice, lemon zest, and water. Stir to combine. Bring the mixture to a simmer over medium heat, stirring constantly. Reduce the heat to medium-low and cook for another 5 minutes or until the mixture thickens. The blueberries should also be slightly popped. Remove it from the heat and set it aside to cool.
Mix the dry ingredients. Whisk the oats, brown sugar, cinnamon, and salt in a large mixing bowl.
Make it crumbly. Add butter to the dry ingredients. Use a pastry cutter or two forks to mash the butter until the mixture is crumbly and sand-like. There shouldn’t be any large chunks of butter left.
To Assemble the Bars
Press the mixture. Set aside 2 cups of the mixture. Add the remaining mixture to the prepared pan. Spread it out and press it down into an even layer. Spray your hands with a little bit of cooking spray to keep the mixture from sticking to your hands. Bake the crust. Pop the baking pan into the oven for 10 minutes. Remove it from the oven.
Add the filling. Carefully spread the fruit filling over the crust using a spoon. Sprinkle the reserved crumb mixture on top. Gently pat it down. Place the pan in the oven and bake for another 40 to 50 minutes or until golden brown. Serve. Remove the baking pan from the oven. I know it’s difficult to wait, but let the bars cool completely before cutting.
Tips For Success
Don’t worry if you’ve never made crumb bars before. Here are several tips to make sure they come out perfectly:
Line the pan. Lining the baking pan with parchment paper will make for easier slicing and clean-up once the bars are baked. Use a silicone spatula. It’s important to stir the filling frequently as it cooks so that nothing sticks and burns. Using a silicone spatula will help you scrape the bottom and sides of the pot completely. Use the middle rack. Never bake on the lowest oven rack. It tends to be one of the hottest areas in the oven and won’t bake (or cook) your food evenly. Always choose the middle rack for the best results.
Make These Crumble Bars Your Own
Use different fruit. Combining your favorite berries like strawberries, blackberries, raspberries, pitted cherries, and blueberries makes a uniquely different filling. If berries aren’t in season, try my rhubarb bars! Use compote. An organic or high-quality fruit compote can help you throw this recipe together even quicker if you’re in a hurry. You’ll need about 2 cups or 16 ounces. Make it nutty. Adding ½ cup of finely chopped almonds, walnuts, or pecans to the dry ingredients for the crumbly mixture will give these sweet treats a nutty crunch. Add chocolate chips. Sprinkling ¼ – ½ cup of white or dark chocolate chips onto the top of bars before baking will give these bars extra flavor.
Serving Suggestions
These blueberry crumb bars are perfect on their own for a lightly sweet and fruity snack. They’re also fantastic with a large scoop of my no-churn vanilla ice cream or cinnamon ice cream. For something a bit simpler, drizzle a bit of caramel sauce on top or add a dollop of freshly whipped cream.
Finally, your favorite tea, coffee, milk, or hot chocolate are all great drink options!
Storage & Freezing Tips
There are several methods for storing blueberry crumb bars. Choose whichever works best for you:
Counter. These blueberry crumb bars can be stored in an airtight container (away from heat and sunlight) for 4 to 5 days. Fridge. If your area is humid or you want to keep them longer, refrigerate the bars in an airtight container for up to 7 days. Set them on the counter for 10 to 15 minutes until they come down to room temperature before serving. Freezer. To freeze them, individually wrap each bar in plastic wrap twice and then in foil once. Transfer the wrapped bars into a freezer-friendly bag or container for up to 3 months. Thaw them overnight in the fridge or set them on the counter until they come to room temperature.
