Yes, if you have dried (or fresh) oregano in your pantry, you can use it in your recipe that requires fresh (or dried) oregano. However, you will need to adjust the measurement because the dried version is more potent than the fresh one. When I substitute fresh oregano for dried oregano, I use one tablespoon of fresh Greek or Mexican oregano for every teaspoon of the dried form. Meanwhile, I add the same amount of fresh Greek or Mexican oregano as the recipe needs when using the dried version and then just add more as and when needed.