I just started using this feed a few months ago and haven't looked back! You can really smell the oregano when you open up the bag! I was gonna suggest this to OP too as an option.That’s why I like using Nutrena NatureWise feeds, they have essential oils in them already including oregano. I know fresh would be better but for those who aren’t able to provide fresh I think it is a decent alternative.
I actually really love this feed and am surprised I don't hear more people talking about it. OP, if you're having trouble getting them to eat the oregano, check out this feed.