Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking pan.

In a large bowl, mix together the melted butter and granulated sugar until well combined.

Add the eggs one at a time, mixing well after each addition, followed by the vanilla extract.

In another bowl, sift together the flour, cocoa powder, and salt. Gradually add the dry ingredients to the wet mixture, stirring until just combined.

Pour half of the brownie batter into the prepared pan and spread evenly. Layer half of the halved Oreo cookies over the batter.

Pour the remaining brownie batter on top of the Oreos and spread evenly. Top with the remaining Oreo halves.

Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted comes out mostly clean (a few moist crumbs are okay).

Allow the brownies to cool in the pan before cutting into squares and serving.