A robot controller controls a robot to maintain balance in response to an external disturbance (e.g., a push) on level or non-level ground. The robot controller determines a predicted stepping location for the robot such that the robot will be able to maintain a balanced upright position if it steps to that location. As long as the stepping location predicted stepping location remains within a predefined region (e.g., within the area under the robot's feet), the robot will maintain balance in response to the push via postural changes without taking a step. If the predicted stepping location moves outside the predefined region, the robot will take a step to the predicted location in order to maintain its balance.