Preheat your oven according to the temperature listed on your brownie mix (usually 350°F).

In a large bowl, whisk together the brownie mix, 2 eggs, ⅓ cup oil, and ⅓ cup milk until smooth and glossy.

Lightly grease an 8x8 or 9x9 baking pan. Pour in half the batter and spread it evenly.

Layer Oreo cookies with orange filling on top—about 16–20, depending on pan size. Don’t press them down.

Pour the remaining brownie batter over the cookies and spread it gently to cover them completely.

Bake for 28–35 minutes or until a toothpick inserted comes out with moist crumbs (no raw batter).

Let the brownies cool completely on a wire rack before frosting.

In a bowl, mix white or vanilla frosting with orange gel food coloring until evenly tinted.

Spread milk chocolate frosting over the cooled brownies in an even layer.

Use a piping bag or zip-top bag to drizzle or pipe the orange frosting on top in swirls, spiderwebs, or spooky zigzags.