You are better off cooking rice porridge over the stove as it cooks very fast. However, if you want to try it in the microwave oven, you can do so provided you stand by the oven to skim off any foam that forms during the cooking process. To do that you need a deep heavy duty glass bowl like a pyrex, add water and turn the knob to high for about 10 minutes, watching it to make sure it doesn't spill over. Remove any foam that forms and continue cooking until soft, adding water if necessary and increasing the time in the process.