Preheat your oven to 350°F (175°C) and prepare a 13x9-inch baking pan with parchment paper and grease.

In a large mixing bowl, whisk together sugar, flour, cocoa, salt, and baking soda until combined.

In a separate bowl, mix oil, eggs, and vanilla until smooth. Gradually add to dry mixture until just moistened.

In another bowl, combine sugar, flour, baking soda, and pumpkin pie spice. In a separate bowl, fold together pumpkin puree and eggs until smooth. Combine both mixtures until just blended.

Spread half of the brownie batter evenly in the prepared pan, then dollop half of the pumpkin mixture over it. Repeat with the remaining batters.

Create a swirl effect using a knife or toothpick through layers of brownie and pumpkin batter.

Bake for 25 to 30 minutes until a toothpick comes out clean. Let cool slightly before lifting out onto a cutting board.

Once cool enough to handle, cut into squares or bars and serve.