  Green's function Monte Carlo calculations of magnetic dipole, electric
quadrupole, Fermi, and Gamow-Teller transition matrix elements are reported for
A=6,7 nuclei. The matrix elements are extrapolated from mixed estimates that
bracket the relevant electroweak operator between variational Monte Carlo and
GFMC propagated wave functions. Because they are off-diagonal terms, two mixed
estimates are required for each transition, with a VMC initial (final) state
paired with a GFMC final (initial) state. The realistic Argonne v18 two-nucleon
and Illinois-2 three-nucleon interactions are used to generate the nuclear
states. In most cases we find good agreement with experimental data.
