These oatmeal raisin sourdough cookies are soft, chewy, and loaded with cozy flavor in every bite. The subtle tang from the sourdough discard pairs perfectly with sweet raisins and hearty oats for a comforting, homemade treat.
Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper or a silicone mat.
In a medium bowl, whisk together the flour, rolled oats, baking soda, baking powder, and salt. Set aside.
In a large bowl, cream the softened butter with the white sugar and brown sugar until smooth and slightly fluffy. Mix in the egg, vanilla, and sourdough discard until combined.
Add the dry ingredients to the wet ingredients and fold gently until just combined — don’t overmix. Fold in the raisins.
Scoop dough by heaping tablespoons (or use a small cookie scoop) onto the prepared baking sheet, spacing about 2 inches apart. Slightly flatten each ball with your fingers for even baking.
Bake 10–12 minutes, until the edges are lightly golden but centers still look soft. Let cookies cool 5 minutes on the baking sheet, then transfer to a wire rack to finish cooling.
Store cooled cookies in an airtight container for up to 4 days, or freeze for longer storage.