A number of $\drbar$ renormalization constants in softly broken
\susy{}-\qcd{} are evaluated to three-loop level: the wave function
renormalization constants for quarks, squarks, gluons, gluinos, ghosts,
and \epscalar{}s, and the renormalization constants for the quark and
gluino mass as well as for all cubic vertices. The latter allow us to
derive the corresponding $\beta$ functions through three loops, all of
which we find to be identical to the expression for the gauge $\beta$
function obtained by Jack, Jones, and North~\cite{Jack:1996vg} (see also
Ref.\,\cite{Pickering:2001aq}). This explicitely demonstrates the
consistency of \dred{} with \susy{} and gauge invariance, an important
pre-requisite for precision calculations in supersymmetric theories.