We have this question alot - is it okay to drink oolong tea while breastfeeding....
Here is the bottom line, it has become obvious to me that some women drink the oolong tea to help lose weight that was gained during the pregnancy.
While oolong is much safer than medication to loose weight, it is high in caffeine content. Oolong helps you to loose weight by increasing your metabolism and making your digestive system work more efficiently.
Anything you consume - drink - or eat while breastfeeding is potentially passed to your child. So the high caffeine content in oolong is not advised while you are breastfeeding.
I would stick to safe herbal teas that are okayed for pregnancy. You can read about those types of teas here