I’m sharing my Lemon Crumble Bars Recipe that layers a buttery oatmeal crust, a lemon filling, and a generous crumble topping, and I’ll reveal the simple trick I use to keep the filling perfectly set.

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I stumbled onto these Lemon Oatmeal Crumble Bars when I needed something bright but not fussy, and they surprised me. The tang of lemon zest cuts through a dense, oat-forward base made with old fashioned rolled oats, while a generous crumble on top gives it that slightly messy, addictive chew.

I keep calling them my favorite Oatmeal Crumble Bars, even though I change little things every time, and the way the Lemon Crumble Topping breaks apart is the reason people ask for seconds before dessert’s even plated. They look simple, but there’s a little trick to the texture that always gets reactions.

Ingredients

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Rolled oats add chewy texture, fiber, whole grain goodness, gentle nutty flavor.
Flour gives structure, carbs for bulk, snacks feel satisfying not very nutritious.
Brown sugar makes it moist, gives caramel notes, sweet warmth and depth.
Cold butter makes crumbly, rich texture and buttery flavor, it adds fat.
Eggs bind the bars, add protein, lift and give a tender bite.
Lemon juice and zest bring bright sourness, fresh citrus zing, balances sweet.
Vanilla adds warm aroma, powdered sugar dusting looks pretty and sweet.

Ingredient Quantities

2 cups old fashioned rolled oats

1 3/4 cups all purpose flour

1 cup packed light brown sugar

1/2 cup granulated sugar (for crust)

1 teaspoon baking powder

3/4 teaspoon fine salt divided

1 cup unsalted butter cold and cubed (2 sticks)

1 teaspoon vanilla extract

3 large eggs room temperature

1 1/4 cups granulated sugar (for lemon filling)

1/3 cup all purpose flour (for filling)

1/2 cup fresh lemon juice about 2 to 3 lemons

2 tablespoons lemon zest from about 2 lemons

powdered sugar for dusting optional

How to Make this

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1. Preheat oven to 350 F and line a 9×13 inch pan with parchment leaving an overhang for easy lifting.

2. In a large bowl combine 2 cups old fashioned rolled oats, 1 3/4 cups all purpose flour, 1 cup packed light brown sugar, 1/2 cup granulated sugar (for crust), 1 teaspoon baking powder and 1/2 teaspoon of the fine salt. Add 1 cup cold unsalted butter cubed and 1 teaspoon vanilla extract and work it in with a pastry cutter or pulse in a food processor until the mix is sandy with some pea sized crumbs. Reserve about 1 1/2 to 2 cups of this mixture for the topping, press the rest firmly into the prepared pan using the bottom of a measuring cup.

3. Bake the pressed crust 12 to 15 minutes or until it’s set and just starting to turn golden, you want it cooked but not browned too much.

4. While the crust bakes whisk the filling: beat together 3 large room temperature eggs and 1 1/4 cups granulated sugar (for lemon filling) until smooth, then whisk in 1/3 cup all purpose flour (for filling) and the remaining 1/4 teaspoon fine salt. Zest first and then add 2 tablespoons lemon zest, squeeze about 1/2 cup fresh lemon juice (about 2 to 3 lemons), remove seeds if any. Mix until fully combined, don’t overbeat.

5. Pour the lemon filling over the hot parbaked crust, spread gently and evenly.

6. Sprinkle the reserved oat crumble over the filling, pressing a few larger pieces lightly into the filling but leave some loose for a nice texture.

7. Bake for 20 to 25 minutes more, until the filling is mostly set and the top is lightly golden. Don’t overbake or the filling will crack.

8. Cool completely on a wire rack, then chill in the fridge at least 2 hours or overnight for the cleanest slices, trust me it’s worth it.

9. Use the parchment overhang to lift the slab out, dust with powdered sugar if you want, then cut into bars with a sharp knife (run the knife under hot water and wipe between cuts for neater pieces).

10. Store bars loosely covered at room temp for up to 2 days or in the fridge up to 5 days, and warm briefly before serving if you prefer them softer.

Equipment Needed

1. 9×13 inch baking pan lined with parchment paper with an overhang for easy lifting
2. Large mixing bowl
3. Medium bowl for the lemon filling
4. Measuring cups and spoons
5. Pastry cutter or small food processor
6. Flat bottomed measuring cup or glass to press the crust firmly
7. Whisk and rubber spatula
8. Wire cooling rack, youll want it for clean cooling
9. Sharp knife and a cup of hot water to wipe the blade between cuts

FAQ

How do I get clean, neat slices? Let the bars cool completely, then chill in the fridge for 1 to 2 hours so the lemon layer firms up. Line the pan with parchment so you can lift the whole slab out. Use a very sharp knife, dip it in hot water and wipe it dry between cuts. It helps to press the crust firmly into the pan before baking so edges dont fall apart.

Can I use bottled lemon juice instead of fresh? You can, but fresh is much brighter and the zest in the recipe really needs fresh lemons. If you must use bottled, taste first and maybe add a little extra zest to boost flavor. Texture won't change much but it wont taste as lively.

My filling was still jiggy after baking, what went wrong? The filling should be set at the edges and just slightly jiggle in the center when it comes out. If it's still very loose bake a few more minutes, check every 3 to 5 minutes so you dont over bake and crack it. Cooling and then chilling will finish the set. Also make sure eggs are room temp so they emulsify properly.

Can I make these ahead and how should I store them? Yes. Store in an airtight container in the fridge for up to 4 to 5 days. You can freeze cut bars for up to 3 months, wrapped tightly; thaw in the fridge. Dust with powdered sugar right before serving so it doesnt melt.

Any good swaps for gluten free or less sugar? For gluten free use a 1 to 1 gluten free all purpose flour and certified gluten free oats, the texture will be a bit different but still tasty. To cut sugar try reducing the lemon filling sugar by 25% and taste, but know less sugar can make the filling looser and more tart. Brown sugar in the crust gives chew, so replacing it with all white sugar will change the texture.

Why is my crust greasy or too crumbly? Make sure the butter is cold and cut into pea sized bits before you press it in, that gives a better crumble. If you overwork the dough it gets greasy, so mix just until crumbs form. Pre-baking the base until it's lightly golden helps it hold up under the lemon layer.

Lemon Oatmeal Crumble Bars Recipe Substitutions and Variations

Unsalted butter (1 cup): swap with solid coconut oil or vegan stick butter 1:1. Use chilled so the crust still flakes, expect a hint of coconut if you choose coconut oil, and the texture can be a tad more crumbly.
3 large eggs: make flax “eggs” for each egg mix 1 tbsp ground flaxseed with 3 tbsp water, rest 5 minutes. Works for binding but the lemon filling will be a bit less silky than with real eggs.
All purpose flour (1 3/4 cups): use a cup-for-cup gluten free flour blend 1:1. If your blend lacks xanthan gum add about 1/4 tsp xanthan per cup to help hold the bars together.
Fresh lemon juice (1/2 cup): bottled lemon juice can be used 1:1, or swap with lime juice if you want a sharper, different flavor. For extra tartness add a pinch (about 1/8 tsp) of citric acid.

Pro Tips

1) Keep the butter rock cold for the crust and topping, work it in quickly with a pastry cutter or pulse in the processor so you still have some pea sized bits. Those little bits melt while baking and give you a flaky, not greasy, texture.

2) Parbake the pressed crust until it is just set and barely golden, not dark. If you overbake it the filling won’t bond and the bars will separate or crack, so check early and trust the “set but slightly soft” feel.

3) Zest first, then juice the lemons, and strain the juice if you see any pulp or seeds. Also use room temperature eggs so the filling mixes smoothly and doesn’t trap air that can make it crack while baking.

4) Chill the finished bars thoroughly before cutting, and when slicing heat a sharp knife under hot water, wipe it dry between cuts. This gives you clean edges every time, and if you want softer bars just let them sit at room temp a few minutes before serving.

Lemon Oatmeal Crumble Bars Recipe

Recipe by Francis Mead

0.0 from 0 votes

I'm sharing my Lemon Crumble Bars Recipe that layers a buttery oatmeal crust, a lemon filling, and a generous crumble topping, and I'll reveal the simple trick I use to keep the filling perfectly set.

Servings

servings

Calories

348

kcal

Equipment: 1. 9×13 inch baking pan lined with parchment paper with an overhang for easy lifting
2. Large mixing bowl
3. Medium bowl for the lemon filling
4. Measuring cups and spoons
5. Pastry cutter or small food processor
6. Flat bottomed measuring cup or glass to press the crust firmly
7. Whisk and rubber spatula
8. Wire cooling rack, youll want it for clean cooling
9. Sharp knife and a cup of hot water to wipe the blade between cuts

Ingredients

2 cups old fashioned rolled oats
1 3/4 cups all purpose flour
1 cup packed light brown sugar
1/2 cup granulated sugar (for crust)
1 teaspoon baking powder
3/4 teaspoon fine salt divided
1 cup unsalted butter cold and cubed (2 sticks)
1 teaspoon vanilla extract
3 large eggs room temperature
1 1/4 cups granulated sugar (for lemon filling)
1/3 cup all purpose flour (for filling)
1/2 cup fresh lemon juice about 2 to 3 lemons
2 tablespoons lemon zest from about 2 lemons
powdered sugar for dusting optional

Directions

Preheat oven to 350 F and line a 9×13 inch pan with parchment leaving an overhang for easy lifting.
In a large bowl combine 2 cups old fashioned rolled oats, 1 3/4 cups all purpose flour, 1 cup packed light brown sugar, 1/2 cup granulated sugar (for crust), 1 teaspoon baking powder and 1/2 teaspoon of the fine salt. Add 1 cup cold unsalted butter cubed and 1 teaspoon vanilla extract and work it in with a pastry cutter or pulse in a food processor until the mix is sandy with some pea sized crumbs. Reserve about 1 1/2 to 2 cups of this mixture for the topping, press the rest firmly into the prepared pan using the bottom of a measuring cup.
Bake the pressed crust 12 to 15 minutes or until it's set and just starting to turn golden, you want it cooked but not browned too much.
While the crust bakes whisk the filling: beat together 3 large room temperature eggs and 1 1/4 cups granulated sugar (for lemon filling) until smooth, then whisk in 1/3 cup all purpose flour (for filling) and the remaining 1/4 teaspoon fine salt. Zest first and then add 2 tablespoons lemon zest, squeeze about 1/2 cup fresh lemon juice (about 2 to 3 lemons), remove seeds if any. Mix until fully combined, don't overbeat.
Pour the lemon filling over the hot parbaked crust, spread gently and evenly.
Sprinkle the reserved oat crumble over the filling, pressing a few larger pieces lightly into the filling but leave some loose for a nice texture.
Bake for 20 to 25 minutes more, until the filling is mostly set and the top is lightly golden. Don't overbake or the filling will crack.
Cool completely on a wire rack, then chill in the fridge at least 2 hours or overnight for the cleanest slices, trust me it's worth it.
Use the parchment overhang to lift the slab out, dust with powdered sugar if you want, then cut into bars with a sharp knife (run the knife under hot water and wipe between cuts for neater pieces).
Store bars loosely covered at room temp for up to 2 days or in the fridge up to 5 days, and warm briefly before serving if you prefer them softer.

Notes

Below you’ll find my best estimate of this recipe’s nutrition facts. Treat the numbers as a guide rather than a rule—great food should nourish both body and spirit. Figures are approximate, and the website owner assumes no liability for any inaccuracies in this recipe.