Future planetary exploration missions will use rovers to perform tasks in rough terrain. Working in such conditions, a rover could become trapped due to loss of wheel traction, or even tip over. The Jet Propulsion Laboratory has developed a new rover with the ability to reconfigure its structure to improve tipover stability and ground traction. This paper presents a method to control this reconfigurability to enhance system tipover stability. A stability metric is defined and optimized online using a quasi-static model. Simulation and experimental results for the Sample Return Rover (SSR) are presented. The method is shown to be practical and yields significantly improved stability in rough terrain.