  Higgs production from gluon fusion is sensitive to the properties of heavy
colored fermions and to the Yukawa couplings, (Y_F M_F)/v, of these particles
to the Higgs boson. We compute the two--loop, ${\cal O}((Y_F M_F)^3/v^3)$
contributions of new high mass fermions to Higgs production. In the Standard
Model, these contributions are part of the well-known electroweak corrections
and are negligible. However, in models with TeV scale fermions, such as top
partner or composite models, Yukawa corrections are enhanced by effects of
${\cal O}((Y_F M_F)^3/v^3)$ and are potentially significant due to the large
mass of the new quarks. We examine the size of these top partner Yukawa
corrections to Higgs production for parameter choices which are allowed by
precision electroweak constraints.
