My blueberry oatmeal bars are bursting with fresh blueberries! I’ve mixed them with a key lime pie filling and sandwiched all that blueberry lime yumminess between two layers of oatmeal crumble. Easy to make and perfect for bringing to a party.
One of my favorite things about summer are all the fresh blueberries! I make pies and drinks and crisps and now blueberry oatmeal bars.
These bars are so good and so easy that I’ve made them three times in the past few weeks. First, to thank my neighbors for helping clean up after our naughty cat while we were away. (He knocked over some water on our wood floor.) Second, to bring to a summer get-together with my parents and in-laws. And, third, just for us to enjoy.
I mean, how could you go wrong? Blueberries + the filling I use in my key lime pie + oatmeal crumble. Simple is the word!
How to Make Blueberry Oatmeal Bars
A few tips to start:
- Use a piece of parchment paper or foil to line the pan so that the bars are easy to remove.
- Make sure your butter is softened but not melty. This way it will be easy to incorporate but the crust won’t get greasy
- Fully chill the bars before trying to cut them. This isn’t strictly necessary but it does make cutting neat bars much simpler.
Making the Oatmeal Crumble
Preheat the oven and bring it up to temperature.
Once your butter is softened (which will take 10-15 minutes if you cut it up into tablespoons as shown), stir together the oats, sugar, and flour in a bowl. Then add the butter and work it in until you have crumble.
Remove 2 – 2 1/2 cups for the topping and then take the remaining crumble and press it into your 9 x 13 pan. I like to use the bottom of the measuring cup to make it nice and flat. Bake the crust for 10 minutes.
Can you substitute in quick oats for the old-fashioned rolled oats?
Yes! The texture will be different since quick oats are smaller and not as chewy; however, I find they work just fine.
Finishing the Blueberry Oatmeal Bars
While the crust is baking, juice and zest your limes then mix the lime juice and zest with condensed milk and two egg yolks. This needs to sit for 5-10 minutes. Which is perfect since it will be done when the crust is out of the oven.
When the crust comes out, scatter the blueberries over and then dollop the lime filling over them. Even it all out with a silicone spatula, but don’t be too worried about making it all smooth. Next, put the bars back in the oven to set the filling. Then back out for the topping.
Scatter the topping over the bars and bake until it is browned and the filling fully set, 30 minutes.
Cool the bars in the pan. Once they are room temperature (or nearly), which is about an hour, run a knife along the edges of the bars which are against the pan. Then lift up the bars from the parchment sling and move them to a cutting board.
At this point you can cut them into squares, though they may squish a bit since they’ll still be soft. Or put the bars in the fridge to fully chill, 3-4 hours to overnight, then use a long knife to make cuts straight down and wipe the knife in between cuts.
What Makes These Oatmeal Bar Cookies So Simple?
First, blueberries are one of the easiest fruits to work with. They are just wash and go. (With a quick once over to check for bad berries.)
Second, the oatmeal crumble is used both for the crust and for the topping. So instead of four parts of the recipe to prepare (and one of those is simply washing berries), you only have three.
Third, key lime pie filling. As long as you don’t get too creative and start substituting ingredients willy nilly, this is the definition of impossible to mess up. (Though, hey if you want go your own way, I’d love to hear if it worked or not.)
Can You Use Frozen Blueberries in Blueberry Bars?
Yes, you can.
Defrost them completely and drain the liquid before you add them to the crust. Then be careful not to mix the lime filling into the blueberries too much since frozen blueberries tend to bleed and make everything blue. The bars will taste the same either way, but they are prettier when you have the contrast of the light filling and the dark berries.
How long do Blueberry Oatmeal Bars keep?
Since they are filled with a custard like filling, keep the blueberry bars in the refrigerator.
They will stay good for 4-5 days. Though by day 5, they will be a little soggy. Fine for leftovers to nibble on, but not so much for serving to guests.
Can the Blueberry Bars be Frozen?
Freeze them on a tray after cutting them into bars. Then seal them in a freezer bag (and you can add a layer of plastic wrap first – so bars, plastic wrap, bag – for extra insurance). They will keep for 2-3 months.
More Great Bar Cookies
- Meyer Lemon Raspberry Bars
- Apple Crisp Bars with Butterscotch Sauce
- Raspberry Orange Streusel Bars
- Chocolate Chip Butterscotch Bars
If you try my recipe for Blueberry Lime Oatmeal Bars, I would love to hear from you in the comments with your experience and rating! You can connect with me by subscribing to my emails (see the form in the sidebar or below the recipe card), liking my FACEBOOK page, or by following me on PINTEREST.
– Happy Baking, Annemarie
Blueberry Lime Oatmeal Crumble Bars
- 2 cups (10 oz) all-purpose flour
- 2 cups (6 1/2 oz) old fashioned oats
- 1 cup packed, (6 1/2 oz) light brown sugar
- 1 tsp baking powder
- 2 tsp vanilla extract
- 1/2 tsp table salt
- 16 tbsp (2 sticks, 8 oz) unsalted butter, softened
Blueberry Lime Filling
- 1 12 oz can sweetened condensed milk
- 1/2 cup lime juice
- 2 tsp lime zest
- 2 egg yolks
- 12 oz (about 2 cups or 1 dry pint) blueberries, washed and blotted dry
- Preheat oven to 350F. Make a sling of parchment paper for a 9 x 13 baking dish, so that the ends hang over the long sides of the dish. Grease the dish well with butter or baking spray.
- In a large bowl, mix together flour, oats, brown sugar, baking powder, vanilla, and salt. Cut the butter into tablespoon sized pieces. Add the butter to the bowl and mix with your fingers until the butter is incorporated and the mixture looks crumbly.
- Remove 2 - 2 1-2 cups of crumble and reserve for the topping. Pour the remaining crumble into the prepared baking dish. Press evenly into the dish, using the bottom of a cup or other wide, flat item.
- Bake for 10 minutes.
Blueberry Lime Filling
- Mix together the condensed milk, lime juice and zest, and egg yolks until smooth and full combined. Let the filling sit and thicken for 5-10 minutes.
- Drop the blueberries evenly over the hot crust. Dollop the lime filling over the blueberries and spread it out with a spatula. Bake the crust and filling for 7-8 minutes.
- Now sprinkle the reserved crumble topping over everything. Then bake for 30-35 minutes, until the filling is bubbly and the topping is golden brown.
- Cool in the pan for 1 hour. Run a knife along the edges of the pan. Pull the bars out of the pan with the sides of the parchment paper and transfer them to a cutting board.
- At this point you can cut the bars, though they will be soft still, or refrigerate them for at least 4 hours to firm them up. To cut use a long knife and slice straight down, wiping off the blade as needed.
- Storing: Bars can be stored in the refrigerator for 4-5 days or in the freezer for 2-3 months.
- Substitutions: Lemon juice can be substituted for the lime juice. Also, though I prefer the texture of the old-fashioned oats, you can use quick oats if needed.