Preheat oven to 350F. Set rack in middle position. Liberally spray 8x8 inch square baking pan with nonstick baking spray, then line it with parchment paper, leaving at least 2 inches of overhang.
In a medium bowl, using your hand mixer, add melted butter and both sugars. Mix on medium speed.
Add eggs one at a time, mixing after each addition to incorporate well.
Add in oil and vanilla extract.
Combine flour, cocoa powder, and salt in a small bowl.
Reduce mixer speed to low and add dry ingredients in two intervals. Mix until just incorporated. Stir in crushed Oreos by hand.
Add brownie batter to prepared pan.
Bake until edges are just set and the center is still soft, about 18 minutes.