After noticing that the cuts on my Bosch CM10GD miter saw have been slightly out of square I found the problem in an unexpected place.  The issue was not an adjustment.  A section of the fixed fence on one side had curved a bit where that casting has less support. 

Working the piece on coarse sandpaper did not entirely solve the problem and caused concerns about having the whole left side too low.  The solution was ordering a new section of the fence, which was surprisingly painless.  Bosch's Website is intuitive and the reasonable cost was a pleasant surprise.