Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper.

Mix dry ingredients: In a large bowl, whisk together the oats, flour, raisins, cranberries, baking powder, baking soda, and salt.

Beat butter and sugars: In a separate large bowl, beat the softened butter, dark brown sugar, and granulated sugar together with an electric mixer until light and fluffy.

Add wet ingredients: Beat in the egg, ground cinnamon, and vanilla extract until smooth.

Combine wet and dry: Slowly add the dry oat mixture into the butter mixture. Beat or stir just until combined.

Scoop the dough: Drop rounded tablespoons of dough onto the prepared baking sheets. Leave about 2 inches of space between each cookie so they can spread.

Bake: Bake for 12 to 16 minutes until the edges are golden brown, but the centers are still soft.

Cool: Let the cookies cool completely on the baking sheets before eating.