If OG/Idaho Mike Iupati is still around at 27, I think the Cowboys will take him. He is 6'5" and 325# and can perhaps play tackle as well as guard. The Cowboys will need to replace most of their OLine in the next 3 years and Iupati seems to be the best player at this spot.
There will be very few free agents available this year, due to the CBA. So I am thinking the QBs in this draft will all move up and perhaps Iupati will be available.
If he is not available then Charles Brown or Jason Fox should be (both OTs).