An 18 year old is dateing a 16 year in Oregon is this agisnt the law?

Dating isn't the problem; sex with minors is.

I believe the age of consent in Oregon is 18.
But there is no problem if you are dating her, as long as you don't have sex with her, because if you do, it would be considered Statutory rape

There is no law anywhere in the US that governs dating. The laws all refer to sexual activity. Since the age of consent is 18, you can't have sex with her, but, as long as her parents are OK with it, you can date.