"previously talked about" is grammatically correct and can be used in written English.
It is typically used to refer to something that was discussed or mentioned earlier in the text or conversation. Example: As previously talked about, the company's profits have been steadily increasing over the past year.
We previously talked about this project when you announced it almost two years ago.
H.P. has previously talked about offering these pattern-finding capabilities in its computer servers.
I want the LHC to be remembered for something that we have never previously talked about.
Word Lens, the clever printed-text live translator we've previously talked about in App Smart, has been updated.
Best Buy declined a request to be interviewed, but Bishop has previously talked about the growing financial burden of the recycling program.
The measure previously talked about in the Assembly called for an increase of nearly one percentage point on anyone who earns $1 million or more annually.
You can start with an interesting story about something that happened to you, something you were previously talking about, or something cool you just heard on the news.
Conversations do not have to follow a logical path, they often go off on tangents or jump to new topics that have nothing to do with anything you were previously talking about so do not worry too much about finding ways to link conversations together.
She had previously talked little about her past, and now memory loss was setting in.
We've previously talked here about strained parent-child relationships in the context of tensions between siblings, the ones who step up to care for parents and resent those who feel they can't.
Monteith had previously talked frankly about struggling with addiction since he was a teenager.
