Preheat your oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.
In a large bowl, combine the cake mix, eggs, vegetable oil, and milk. Mix until well combined and smooth.
1 box yellow cake mix
Spread the batter evenly into the prepared baking pan.
Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
Let the bars cool completely in the pan on a wire rack.
Once cooled, spread the vanilla frosting evenly over the top. Decorate with sprinkles if desired.
1 box yellow cake mix
Cut into bars and serve.
Notes
These cake mix cookie bars are incredibly versatile. You can customize them by adding chocolate chips or different flavor extracts to the batter. For a festive touch, use colored frosting and sprinkles for holidays!