Recipe for making an oil infusion of Oregano (the herb).
I like to cook with Oregano and it is easy to grow in a window box.
You may also buy dried Oregano in the store.
http://www.offthegridnews.com/alternative-health/5-simple-steps-to-make-your-own-oil-of-oregano/DO NOTE the additional information on using this oil for non-cooking uses...
As a prepper, this can be made using non-vegetable oils (fats from rendered meats). It will become a salve and not a liquid oil, but still retain the herbal properties.
Finally, note the recommendation to add Grapefruit Oil as a preservative. This would be problematic if you don't have Grapefruit Oil or even grapefruit peels with which to make it.