Today on the twits it was twitted:
COM T&P committees will overlook your open access publications and not count them. Discuss
— I-75 scientist (@jmcin9) June 15, 2015
This is an important issue facing those currently on or about start on the tenure track (TT). The problem with asking this question is that the resulting discussion tends to devolve into arguments between open access (OA) evangelists and the rest of us* as to the necessity etc. of OA. Phrases like "moral imperative" and "OA wackaloon" get bandied about. I don't really want to get into all that again. Bottom line is:
Moral imperatives won't get you tenure.
So, do T&P committees care? Yes. No.
It's going to depend on the institution. The make up of the committee. The culture of the department you're in (letters from your chair and senior faculty carry weight). The field you're in (outside letters also carry weight).
What the T&P committee should care about is the science, not where you've published it.
[Brief pause for tenured readers to catch their breath after laughing.]
We don't live in that world yet. GlamHumping is still a thing remember. As is IF-lust.
My advice? Look to see what recently tenured folks have done. Maybe push that limit a little if you're very pro-OA. But mostly, publish in a variety of places.
But first do good science.
* For the record, I like OA. I've published in OA journals and will continue to. I don't see it as a moral imperative though and don't do OA exclusively.