Oakland rushed for 328 yards in a 59-14 rout of the Broncos on Sunday. Raiders tailback Darren McFadden led the way with 165 yards rushing and three touchdowns.
Smith was with the Broncos last season after being acquired from the New England Patriots just before the start of the year. He played in 13 games and had one sack.
The Broncos released the 6-foot-3, 308-pound Smith in September.
Smith was a sixth-round pick by the Patriots in the 2006 draft out of the University of Nebraska.