'Tenure' is a noun, and 'tenured' is an adjective. There is no verb (one could offer, hold, etc a tenured position).

There seems to be a verb according to the Oxford English Dictionary.
"to tenure v.trans., to provide (someone) with a tenured post."

Thanks. My dictionary and LEO only know the noun "tenure", that's why I asked. But Merriam-Webster (http://www.m-w.com) says:
Main Entry: ten·ured
Pronunciation: 'ten-y&rd
Function: adjective
Date: 1965
: having tenure <tenured faculty members>

I could have looked there before, sorry.

M-W doesn't know the verb, however. (I posted my previous comment before I read Doris' answer.)

I was using the Chambers to confirm my suspicion that there was no verb. If the Oxford says there is, I suppose there is, but I've never heard anyone use 'tenure' that way.

Sue, I told you to throw that Chambers away...
;)

But Doris, the scrabble connection! The definition of 'Sloane Ranger'! For these reasons alone, the dear red volume is immeasurably valuable to me! That's kind of sad, isn't it?!