Pour water into cooker. Place broccoli on rack or trivet in cooker. Lock lid and bring to full pressure. Immediately remove from heat. Quick-release the pressure. Remove broccoli to serving dish. Sprinkle with oil, sesame seeds, and oregano.
*To toast seeds, heat them in a non-stick skillet over medium-low heat, shaking occasionally, until they are evenly golden, about 5 minutes.