Preheat the oven to 350 degrees.
Line a 13x9x2 inch pan with parchment paper with an overlap at the edges.
Prepare your brownie mix according to the package instructions. Spread it evenly onto the parchment paper.
In a large bowl, mix the red velvet cake mix, oil, egg, and milk together until well mixed. It will be a thick batter.
Use a large spoon to plop about 6 or 8 dollops of the red velvet cake mixture on top of the brownie mixture. Space the dollops a few inches apart from each other.
Use a butter knife and swirl the red velvet cake mixture with the brownie mix. Make zig-zag motions too. Do NOT mix the two batters together! Just swirl!
Bake at 350 degrees for 15-20 minutes. Test for doneness with a cake tester to see when it comes out ALMOST clean.
Completely cool the brownies in the pan on a wire rack. Then holding the ends of the parchment paper, lift the brownies onto a board. Cut them into squares.
Store them covered on top of the counter.