My Old-School Secret to the Best Lemon Bars of Your Life

head on shot of a stack of lemon crumb bars on a marble surface.
Credit: Photo: Alex Lepe; Food Styling: James Park Credit: Photo: Alex Lepe; Food Styling: James Park

Crisps and crumbles, with their juicy fruit and sweetened streusel topping, are among the best desserts for spring and summer. I couldn’t wait to start baking crisps until berries are in season, so I’m making these lemon crumb bars to get the party started. If you love both lemon bars and bubbling fruit crisps, this is a sweet treat you’re sure to enjoy.

In this recipe, I mix together a big batch of brown sugar and oat crumbles, pressing a portion into a baking pan as the crust and reserving the rest for the finishing touch. A simple, two-ingredient (plus kosher salt) filling made from juicy fresh lemons and sweetened condensed milk goes on top of the crust and is finished with the crunchy crumbles. These bars are so easy to make and you mix everything together in a single bowl — no stand mixer or food processor required!

Why You’ll Love Lemon Crumb Bars

  • Bright, lemony flavor is front and center in these bars. I stir both fragrant zest and fresh juice into the zingy filling.

  • The brown sugar-oat crumble topping does double-duty as both the bottom crust and crumble topping.

Key Ingredients in Lemon Crumb Bars

  • Lemon: Use both the zest and juice of fresh lemons to give these bars their bright and citrusy flavor.

  • Sweetened condensed milk: This thick, sweet canned milk forms the base of the lemon filling. Don’t confuse sweetened condensed milk with evaporated milk, which is thinner and unsweetened.

  • Oats: Old-fashioned rolled oats have more flavor and chew than the quick-cooking variety, but both work well in this recipe. Combine the oats with all-purpose flour to form the crust and crumbles.

  • Brown sugar: Dark brown sugar has a higher molasses content, which gives it a deeper flavor and more chew than light brown sugar. Either variety will work in this recipe.

  • Baking powder: This leavening agent is added to give the crust and crumble a lighter, less compact texture.

  • Butter: Melted unsalted butter binds the crust and crumble ingredients together.

More Easy Lemon Desserts to Try

Lemon Crumb Bars Recipe

The crunchy oat crumble will make anyone a lemon bar fan.

Prep time 15 minutes

Cook time 35 minutes to 40 minutes

Makes 12

Serves 12

Ingredients

  • 8 tablespoons (1 stick) unsalted butter

  • 3/4 cup packed dark or light brown sugar

  • 3/4 teaspoon baking powder

  • 3/4 teaspoon kosher salt, divided

  • 1 1/4 cups old-fashioned rolled or quick-cooking oats

  • 1 cup all-purpose flour

  • 2 large or 3 medium lemons

  • 1 (14-ounce) can sweetened condensed milk

Instructions

  1. Arrange a rack in the middle of the oven and heat the oven to 350°F. Line the bottom and sides of an 8x8-inch baking pan with 2 sheets of parchment paper, positioning them perpendicular to each other and making sure they are long enough to hang over all four sides by at least 1 inch to form a sling.

  2. Cut 1 stick unsalted butter into 8 pieces and place in a large microwave-safe bowl. Microwave in 20-second bursts until mostly melted, 40 to 60 seconds total. (Alternatively, melt the butter on the stovetop, then pour into a large bowl.)

  3. Add 3/4 cup packed light or dark brown sugar, 3/4 teaspoon baking powder, and 1/2 teaspoon of the kosher salt, and stir to combine. Add 1 1/4 cups old-fashioned rolled or quick-cooking oats and 1 cup all-purpose flour, and stir with a flexible spatula until no dry spots remain. Reserve 1 cup of the mixture for topping.

  4. Transfer the remaining crumble mixture into the baking pan. Pat into an even layer. Bake until fragrant and lightly browned, 12 to 14 minutes. Meanwhile, prepare the lemon filling.

  5. Wipe out the crumble bowl (no need to wash). Finely grate the zest of 2 large or 3 medium lemons (about 2 tablespoons) into the bowl. Juice the zested lemons until you have 1/2 cup, then add to the bowl. Add 1 (14-ounce) can sweetened condensed milk and the remaining 1/4 teaspoon kosher salt, and whisk until smooth.

  6. Pour the filling over the hot crust. Sprinkle the reserved crumble mixture evenly over the filling. Return the baking pan to the oven and bake until the edges are lightly browned and set, 22 to 24 minutes. Place the pan on a wire rack and let cool completely, about 1 1/2 hours. If the filling is softer than desired, refrigerate for 30 minutes once completely cooled to firm up.

  7. Grasping the excess parchment paper, lift the slab out of the pan and place on a cutting board. Cut into 12 pieces.

Recipe Notes

Storage: The bars can be tightly wrapped and stored at room temperature for up to 5 days.