Preheat oven to 350°F. Grease and line a 9″x9″ pan with parchment paper and set aside.
In a large microwave-safe bowl, combine butter and sugar. Microwave for 30 seconds, then remove and stir with a whisk. Repeat process 2 more times. Though granules of sugar will remain, the goal is to get the mixture to a glossy finish.
Allow mixture to cool slightly, then add in eggs one at a time, whisking in between each addition. Whisk until the mixture lightens in color slightly.
Add in cocoa powder, salt, and vanilla extract. Fold in flour until just combined. Last, fold in the Oreo cookie pieces.
Pour mixture into prepared baking pan and bake for roughly 45 minutes, testing for doneness by inserting a knife into the center of the brownies beginning at 40 minutes. It might take up to 55 minutes for them to cook through depending on your oven!
Keywords: oreo brownies, cookies and cream brownies, fudgy oreo brownies