In order to make menu action with text "foo & bar" you need to escape '&' like this action->setText("foo && bar");

On mac if action is places to QMenuBar (http://qt-project.org/doc/qt-5.0/qtwidgets/qmenubar.html#qmenubar-on-mac-os-x), '&' is not shown in system-wide menu, and needs to be double-escaped like:
action->setText("foo &&&& bar");