Oatmeal Plum Bars are that perfect late-summer bake when plums are ripe and juicy. You get a thick buttery crust, a gooey fresh plum layer, and golden oat crumbles on top.
The smell alone is reason enough to make them.
I love using real plums for the filling — they turn jammy and sweet with just a bit of tang, and it gives the bars this warm, rustic homemade taste you can’t get from a jar.
💛 Why I Love This Recipe
These bars showed up in our house when I had a few plums and not much time. It’s now a favorite “throw-together” bake I go back to every season.
- Uses simple pantry ingredients
- That plum layer turns all jammy and sweet
- Oat crumble makes it feel wholesome
- No mixer required
- Great for breakfast or dessert
Servings & Cook Time
Servings: 12 bars
Prep Time: 25 minutes
Cook Time: 35 minutes
Total Time: 1 hour
Macros (Per Serving)
- Calories: 255
- Protein: 3g
- Carbs: 35g
- Fat: 11g
- Fiber: 2g
- Sugar: 19g
Why This Recipe Works (Quick Science)
Fresh plums break down while baking and turn into a thick, sticky filling thanks to natural pectin and the small amount of added sugar and cornstarch. The thick oat mixture acts as both base and topping — the butter binds everything and crisps up into a golden crust. The crust is packed in firmly for structure, while the topping stays loose for that perfect crumbly bite.
Common Mistakes
- Skipping the cornstarch: You need it to thicken the fresh plum juices
- Using underripe plums: They’ll be too firm and sour. Ripe = juicy and sweet
- Overloading the plum layer: Keep it around 1½ cups once chopped for best structure
- Not cooling fully: The filling sets as it cools. If you slice too soon, it’ll fall apart
What You’ll Need
For the Plum Filling:
- 1½ cups ripe plums, chopped (about 4–5 small plums)
- 2 tbsp granulated sugar
- 2 tsp lemon juice
- 1 tsp cornstarch
For the Crust and Topping:
- 1 cup all-purpose flour
- 1 cup old-fashioned rolled oats
- ½ cup packed brown sugar
- ½ tsp baking soda
- ¼ tsp salt
- ½ tsp ground cinnamon (optional)
- ½ cup unsalted butter, melted
- ½ tsp vanilla extract
🧁 How to Make Oatmeal Plum Bars
Step 1: Prepare the Plum Filling
In a small bowl, mix 1½ cups chopped ripe plums, 2 tbsp granulated sugar, 2 tsp lemon juice, and 1 tsp cornstarch. Stir to coat and let sit while you prep the crust.
Step 2: Mix Dry Ingredients
In a large bowl, combine 1 cup all-purpose flour, 1 cup old-fashioned rolled oats, ½ cup packed brown sugar, ½ tsp baking soda, ¼ tsp salt, and ½ tsp cinnamon.
Step 3: Add Butter and Vanilla
Pour in ½ cup melted unsalted butter and ½ tsp vanilla extract. Mix until crumbly and moist.
Step 4: Press the Crust
Press ⅔ of the oat mixture into a parchment-lined 8×8 pan to form a thick, even base.
Step 5: Add Plum Layer
Spread the plum mixture evenly over the crust, leaving a slight border at the edges.
Step 6: Add Crumble Topping
Sprinkle the remaining ⅓ oat mixture over the top of the plums and press gently.
Step 7: Bake
Bake at 350°F (175°C) for 35 minutes, or until golden brown and bubbling at the edges.
Step 8: Cool and Slice
Let cool completely in the pan, then lift out using the parchment and cut into 12 bars.
Leftovers and Storage
Store bars in an airtight container at room temp for 2 days or in the fridge up to a week. Freeze up to 2 months between parchment layers — just thaw and enjoy.
What to Serve With
- Vanilla or honey ice cream
- Fresh whipped cream
- A mug of strong black tea or chai
- Greek yogurt for a less-sweet pairing
FAQ
Can I cook the plums down first?
Yes — if your plums are extra juicy, simmer the mixture for 5–7 minutes until thickened.
Can I leave the skin on the plums?
Totally fine. The skins soften and add great color and flavor.
What kind of plums are best?
Use ripe red or black plums. A mix gives nice depth.
Can I double it?
Yes — use a 9×13 pan and bake for 40–45 minutes.
Wrap Up
Fresh plums take these oat bars to the next level — sticky, jammy, and full of flavor. And with that thick crust and crumble topping, you’re getting everything you want in one bite. Give it a try and let me know how yours turn out in the comments — I’d love to hear about it!