To improve situational awareness in power systems, one useful tool used in control centers is bus (or substation) data contouring. Traditionally, the methods developed have used CPU processing, leading to long contour rendering times that reduce interactivity with the visualization. To improve interactivity and increase the data rate which can be handled, contouring methods utilizing graphical processing units (GPU's) show much promise. This paper proposes a GPU-based contouring algorithm which can easily outperform state-of-the-art CPU-based contouring algorithms. In addition, sample rendering times for a typical power system display, along with comments on the relative advantages and disadvantages of using the CPU and GPU to perform contouring, are provided.