Static postural sway can be quantified as variation in body's center of force (COF) position across time using a plantar pressure plate. We aimed to compare capability of three clinically feasible bipedal tasks to extract the contribution of proprioception to postural stability. We measured the postural sway of 24 healthy volunteers (age range 10.2–17.6 years) with a plantar-pressure plate with three different standing tasks: (1) normal standing, (2) normal standing on soft foam, and (3) feet together standing. Each task was repeated eyes closed to emphasize the contribution of proprioception on maintaining the postural stability. The effect of closing the eyes varied among the tasks, and was greatest in the feet together standing task, possibly due to greater proprioceptive demands in the more difficult tasks. It appears that standing feet together is a potential task for quantifying contribution of proprioception to postural stability.