They added 10 more points in the second quarter to take a 17-0 halftime lead, and were never in danger.
McNair completed 18 of 24 passes for one touchdown and 140 yards; Jamal Lewis ran for one touchdown on 17 carries for 66 yards; and Matt Stover kicked two field goals as Baltimore (9-2) won its fifth straight game.
Ben Roethliberger, who was the victim of a fierce pass rush, went 21-for-41 for 214 yards and two interceptions; Willie Parker was held to 22 yards on 10 carries; while both Nate Washington and Cedrick Wilson made four receptions for 49 yards for the Steelers (4-7).
Pittsburgh was shutout for the second time this season.
Notable deaths of 2014 [PHOTOS]