These Sourdough Monster Cookies are thick, chewy, and packed with peanut butter, chocolate chips, and colorful M&Ms. They’re the perfect way to use up sourdough discard and come together in just 30 minutes - no chill time needed!
I’ve been baking with sourdough for years, and cookies are one of my favorite ways to use up discard. So it’s probably no surprise that I’ve shared over 15 sourdough cookie recipes on the blog.
And with so many favorites to choose from - chocolate chip, oatmeal, peanut butter - I figured, why not combine them all into one sourdough monster cookie recipe?
These sourdough monster cookies are the best of all worlds.
The dough is made with hearty rolled oats, natural peanut butter, and sourdough discard, then packed with chocolate chips and colorful M&M candies for a sweet, nutty, chewy cookie you won’t stop craving.
Even better, they come together in just 30 minutes, and there’s no chilling required before baking.
Trust me, once you try these, they’ll quickly become your new favorite sourdough cookie. I hope you give them a try and enjoy them as much as I do!
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Ingredients & Substitutions
Here are some notes on key ingredients. For a full list of ingredients, check out the recipe card below.
- Sourdough Discard- Adds moisture, a subtle tang, and helps cut down on waste. Use room temperature, unfed discard for best results.
- Natural Peanut Butter- Gives the cookies a soft texture without added oils, sugars, or stabilizers. Stir well before using.
- Butter- Start with softened butter for an easier time mixing the dough.
- Rolled Oats- Rolled or old-fashioned oats add chew and heartiness. Quick oats can work in a pinch, but the texture will be a bit softer and less chewy.
- All-Purpose Flour- Provides structure while keeping the cookies tender. For best results, weigh your flour or use the spoon-and-level method.
- Granulated & Brown Sugar- A mix of both sugars gives the cookies the perfect balance of sweetness and chew.
- Kosher Salt- I use Diamond Crystal Kosher Salt. If using Morton’s or table salt, reduce the amount or weigh it to avoid over-salting.
- Mix-Ins- I like semi-sweet chocolate chips and M&Ms for a pop of color and crunch, but feel free to swap in your favorite add-ins.
Tips for Success
- Measure ingredients by weight. Measuring by weight gives you consistent results every time and helps achieve the perfect texture.
- Use natural peanut butter. It gives the cookies a softer texture and doesn't contain added oils, sugars, or stabilizers. Just give it a good stir first!
- Let the dough rest (if you have time!). Even just 30 minutes of rest before baking helps hydrate the oats and flour.
- Customize. Try using mini M&Ms, dark chocolate chunks, chopped peanuts, or even a sprinkle of flaky salt on top before baking.
- Top with extra M&Ms. Pressing a few extra M&Ms onto each cookie before baking gives them a colorful, bakery-style look.
Here is how to make monster cookies with sourdough discard.
Step 1: Preheat oven. Preheat the oven to 350°F. Line a rimmed baking sheet with parchment paper and set it aside.
Step 2: Mix dry ingredients. In a medium bowl, stir together the rolled oats, flour, kosher salt, baking powder, and baking soda. Set aside.
Step 3: Combine wet ingredients. In a large bowl, use a hand mixer (or stand mixer fitted with the paddle attachment) to beat the softened butter, granulated sugar, and brown sugar until light and fluffy - about 2 minutes. Beat in the egg until well combined. Then mix in the peanut butter, sourdough discard, and vanilla extract. Continue mixing until the mixture is smooth and creamy.
Step 4: Prepare cookie dough. Add the dry ingredients to the wet ingredients and mix on low speed until just combined. Gently fold in the M&M candies and chocolate chips.
Step 5: Portion cookie dough. Scoop heaping 2-tablespoon portions of dough onto the prepared baking sheet, leaving about 2 inches between each cookie to allow for spreading.
Step 6: Bake the cookies. Bake for 14–16 minutes, or until the edges are just starting to turn golden brown and the centers look set but still soft.
Step 7: Cool. Let the cookies cool on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely.
How to Store
Store your sourdough monster cookies in an airtight container at room temperature for up to a week.
For longer storage, you can freeze the baked cookies for up to 6 months. Just let them thaw at room temperature before enjoying.
Want to prep the dough ahead of time? Refrigerate it for up to 2 days to long ferment it or freeze for up to 2 months. I recommend portioning the dough into scoops before freezing for easier baking later.
Are you tired of watching your sourdough discard go to waste?
It’s time to turn excess discard into something delicious with my new ebook - Everyday Sourdough!
Inside, you’ll find 27 tried-and-true sourdough discard recipes that will transform your leftover starter into mouthwatering creations your family and friends will love.
No more guilt about wasting your discard - with Everyday Sourdough, you have endless options to quickly make something amazing anytime.
Let's Connect!
Be sure to leave a comment below if you have any questions. You can also connect with me on Instagram, Facebook, Pinterest, or via email at [email protected].
📖 Recipe
Equipment
- Hand mixer or stand mixer
Ingredients
- 1 ½ cups (120 grams) rolled oats
- 1 ¼ cups (150 grams) all-purpose flour
- ½ teaspoon Diamond Crystal Kosher Salt
- ½ teaspoon baking powder
- ¼ teaspoon baking soda
- ½ cup (113 grams, 1 stick) unsalted butter softened
- ½ cup (100 grams) granulated sugar
- ½ cup (100 grams) brown sugar
- 1 large (50 grams) egg room temperature
- ½ cup (128 grams) natural peanut butter
- ½ cup (100 grams) sourdough starter discard room temperature
- 1 teaspoon vanilla extract
- ½ cup (110 grams) M&M candies
- ½ cup (85 grams) semi-sweet chocolate chips
Instructions
- Preheat the oven to 350°F. Line a rimmed baking sheet with parchment paper and set it aside.
- In a medium bowl, stir together the rolled oats, flour, kosher salt, baking powder, and baking soda. Set aside.1 ½ cups (120 grams) rolled oats, 1 ¼ cups (150 grams) all-purpose flour, ½ teaspoon Diamond Crystal Kosher Salt, ½ teaspoon baking powder, ¼ teaspoon baking soda
- In a large bowl, use a hand mixer (or stand mixer fitted with the paddle attachment) to beat the softened butter, granulated sugar, and brown sugar until light and fluffy - about 2–3 minutes. Beat in the egg until well combined. Then mix in the peanut butter, sourdough discard, and vanilla extract. Continue mixing until the mixture is smooth and creamy.½ cup (113 grams, 1 stick) unsalted butter, ½ cup (100 grams) granulated sugar, ½ cup (100 grams) brown sugar, 1 large (50 grams) egg, ½ cup (128 grams) natural peanut butter, 1 teaspoon vanilla extract, ½ cup (100 grams) sourdough starter discard
- Add the dry ingredients to the wet ingredients and mix on low speed until just combined. Gently fold in the M&M candies and chocolate chips.½ cup (110 grams) M&M candies, ½ cup (85 grams) semi-sweet chocolate chips
- Optionally, let the dough rest for 30 minutes at room temperature before baking to allow the oats to soften. You can also refrigerate it overnight if you want to bake the next day.
- Scoop heaping 2-tablespoon portions of dough onto the prepared baking sheet, leaving about 2 inches between each cookie to allow for spreading.
- Bake for 14–16 minutes, or until the edges are just starting to turn golden brown and the centers look set but still soft.
- Let the cookies cool on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely.
Notes
- Storage: Store completely cooled cookies in an airtight container at room temperature for up to 7 days or freeze for up to 6 months.
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