  The known Lorentz invariant string field theory for open N=2 strings is
combined with a generalization of the twistor description of anti-self-dual
(super) Yang-Mills theories. We introduce a Chern-Simons-type Lagrangian
containing twistor variables and derive the Berkovits-Siegel covariant string
field equations of motion via the twistor correspondence. Both the purely
bosonic and the maximally space-time supersymmetric cases are considered.
