Sourdough Iced Oatmeal Cookie Bars

These sourdough iced oatmeal cookie bars are soft and chewy. They’re like an easy-button version of oatmeal cream pies for a crowd!

Made with sourdough discard and topped with sweet vanilla icing, they’re perfect for lunch boxes, an after-school snack, or cozy dessert.

These easy cookie bars can be made in under an hour. There’s no chilling the batter and no long fermentation time.

They use simple ingredients you already have on hand for that oh-so-nostalgic feeling you get from a delicious oatmeal cookie!

Looking for more sourdough cookie bar recipes? Try my sourdough cowboy cookie bars and classic sourdough oatmeal chocolate chip cookie bars. My sourdough peanut butter oatmeal chocolate chip cookie bars roll 3 of your favorite cookies into 1 thick and chewy cookie bar!

Scroll down for the recipe card, followed by detailed step-by-step instructions (with photos). 

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Sourdough Iced Oatmeal Cookie Bars Recipe

Sourdough Iced Oatmeal Cookie Bars

Annabelle

These sourdough iced oatmeal cookie bars are like an easier version of oatmeal cream pies. Soft and chewy, made with sourdough discard and topped with vanilla icing, they're an easy cookie bar you'll make again and again.

5 from 1 vote

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Prep Time 15 minutes mins

Cook Time 25 minutes mins

Total Time 40 minutes mins

Course Dessert, Snack

Cuisine American

Servings 24 cookie bars

Calories 300 kcal

Ingredients

  

Sourdough Oatmeal Cookie Bars

• ½ cup salted butter 1 stick, melted
• ¾ cup brown sugar packed
• ¼ cup white sugar
• 2 teaspoons vanilla extract
• 1 Tablespoon molasses do not use blackstrap molasses, use light or dark molasses
• 1 egg room temperature
• ½ cup sourdough discard
• 1 teaspoon baking soda
• 1 teaspoon ground cinnamon
• ½ salt
• ¾ cup all-purpose flour
• 2 cups quick oats

Vanilla Icing

• ⅔ cup powdered sugar
• ½ teaspoon vanilla extract
• 3-4 teaspoons milk

Instructions

 

Sourdough Oatmeal Cookie Bars

• Preheat oven to 350℉ (177℃). Line a 9×13 glass baking dish with parchment paper and set aside.
• In a large mixing bowl, combine melted butter, brown sugar, and white sugar. Add vanilla extract, molasses, egg, and sourdough discard. Mix to combine and scrape down the sides of the bowl.
• Add baking soda, ground cinnamon, and salt. Add flour and scrape down the sides of the bowl to combine. Add the oats and mix well.
• Pour the batter into the prepared baking dish and use a spatula to spread evenly to the edges and corners.
• Bake at 350℉ (177℃) for 22-24 minutes until browned all over and the middle is mostly set when you gently shake the pan. See note about baking time and testing doneness.
Key tip: Don't over bake! They secret to soft, chewy cookie bars is to slightly underbake them.

Vanilla Icing

• Once cookie bars are completely cooled, mix up the icing by combining powdered sugar, ½ teaspoon vanilla extract, and milk. Add 3 teaspoons of milk to start and if you want the icing a little thinner, add a 4th teaspoon.
• Spoon the icing onto cooled cookie bars and spread evenly. Cut the cookie bars before the icing cools and hardens to avoid cracks, see note. After slicing, allow the icing to cool and harden before serving.

Notes

Oats – Using quick oats for this recipe makes the bars softer and fluffier. You can use old fashioned oats as well, but pulse them in a blender or food processor first to break them up.

Molasses – Do not use blackstrap molasses for this recipe or your cookie bars may be bitter. Use light or dark molasses for baking. Grandma’s Original Unsulphered Molasses is a good brand to use.

Baking – The cookie bars will get very brown all over from the molasses. It’s not burnt, it just needs to be browned and the center not jiggle when you gently shake the pan. 

To Slice – To cut cookie bars so the icing stays smooth and doesn’t crack, slice them before the icing dries. Spoon on the icing and spread evenly. Use a large sharp knife to slice the cookie bars into squares, running the knife under warm water and drying with a clean dish towel between slices.

To Make Ahead – If wanting to serve these cookie bars the next day, don’t add the icing right away or it will start to soak into the bars overnight. Make the cookie bars and allow to fully cool and cover the pan with plastic wrap. The next day add the icing and slice the bars, allowing the icing to harden before serving. This makes sure you’re serving fresh, beautiful cookie bars!

Something about oatmeal cookies is so homey and nostalgic to me. Oatmeal cookies remind me of grandma’s house and simpler times. Maybe because they’re simple cookies. No fuss or extra ingredients. Just simple, wholesome ingredients combined into delicious cookies.

These cookie bars have that same feel to me. I love how easy they are to mix up and bake. There’s no scooping individual cookies or rotating pans in and out of the oven. Sometimes you just need a quick recipe!

Why you’ll love this recipe

• These sourdough oatmeal cookie bars are simple to make. They use pantry ingredients you already have on hand in an easy one-bowl recipe.
• They’re quick! Just mix, pour, and bake. There’s no chilling the batter or scooping individual cookies. There’s one bake time and you’re good to go.
• It’s a large batch recipe. This recipe makes a generous 9×13 pan that can be sliced into 24 cookie bar squares.

Important Ingredients

Sourdough iced oatmeal cookie bars use pantry staples. The ingredients are simple but take note for:

• Oats – Use quick oats for this recipe to make the bars softer and fluffier. You can use old fashioned oats as well, but pulse them in a blender or food processor first to break them up. If you leave them whole the bars will not be as soft and chewy.
• Molasses – Do not use blackstrap molasses for this recipe or your cookie bars may be bitter. Use light or dark molasses for baking. Grandma’s Original Unsulphered Molasses is a good brand to use and what I use for my recipes.
• Sourdough discard or active sourdough starter – Yes, you can use either one! Since you’re using sourdough discard or starter to enhance the flavor, you can use either one you have on hand.
• Vanilla extract – Maybe I’m biased, but there is nothing like the flavor of homemade vanilla extract. I think it levels up any sweet treat recipe. Any kind of vanilla extract will do, but if you want to kick it up a notch, use homemade. I like this recipe from Natasha’s Kitchen.

A full ingredient list with exact amounts can be found in the recipe card above.

How to Make Sourdough Iced Oatmeal Cookie Bars (Step by Step)

Sourdough Oatmeal Cookie Bars

Step 1: Preheat the oven to 350℉ (177℃). Line a 9×13 glass baking dish with parchment paper and set aside.

Step 2: In a large mixing bowl, combine the melted butter, brown sugar, and white sugar. Add the vanilla extract, molasses, egg, and sourdough discard. Mix to combine and scrape down the sides of the bowl.

Step 3: Add the baking soda, ground cinnamon, and salt. Add the flour and scrape down the sides of the bowl to combine. Add the oats and mix well.

Step 4: Pour the batter into the prepared baking dish and use a spatula to spread evenly to the edges and corners.

Step 5: Bake at 350℉ (177℃) for 22-24 minutes until browned all over and the middle is mostly set when you gently shake the pan. The cookie bars will get very brown all over from the molasses. It’s not burnt, it just needs to be browned and the center not jiggle when you gently shake the pan. 

Key tip: Don’t over bake! They secret to soft, chewy cookie bars is to slightly underbake them.

Allow the cookie bars to cool while you making the icing. You want the cookie bars to be completely cool and fully set before you slice them so you cut clean, precise slices.

Vanilla Icing

Step 1: Once cookie bars are completely cool and throughly set, mix up the icing by combining powdered sugar, ½ teaspoon vanilla extract, and milk. Add 3 teaspoons of milk to start and if you want the icing a little thinner, add a 4th teaspoon.

Step 2: Spoon the icing onto cooled cookie bars and spread evenly. To cut the cookie bars so the icing stays smooth and doesn’t crack, slice them before the icing dries.

How to Make Ahead

Key tip: These sourdough oatmeal cookie bars will start to get soft overnight from the icing soaking into them so I recommend adding the icing the day you’ll be serving them.

To make ahead, bake the cookie bars according to the recipe. Allow to fully cool and cover the pan with plastic wrap overnight. The next day add the icing and slice the bars, allowing the icing to harden before serving.

How to Serve

These sourdough iced oatmeal cookie bars are perfect for an after-school snack with a glass of milk. Or serve alongside a cup of coffee or tea for a cozy treat.

Since it’s a large-batch recipe, these are great for taking to a gathering with friends, packing for a camping trip, or serving when hosting a playdate. They’re versatile and easy to grab and go!

How to Store

These sourdough cookie bars can be stored in an airtight container for up to 3 days. Or cover the baking pan tightly with plastic wrap.

Frequently Asked Questions

These sourdough iced oatmeal cookie bars are delicious, wholesome, and nostalgic. They combine simple ingredients into a cookie bar everyone will love. You’ll be making these again and again!

Remember to leave a rating and comment sharing how you enjoyed this recipe!