We present a construction of modular invariant partition functions for heterotic (0,2) supersymmetric classical string vacua. This generalization of Gepner's construction yields GUT gauge groups E6, SO(10), SU(5) and SU(3) x SU(2) x U(1)', respectively, By calculating the massless spectrum of some of these models we find strong indications that they correspond to (0,2) using vacua discussed recently in the context of CYM/LG phases.