We show a new mechanism for baryogenesis where the reheating temperature can
be smaller than the electroweak scale. The baryon number symmetry is violated
by a dimension nine operator which conserves a baryon parity. A high energy
quark from the decay of a heavy particle, e.g. inflaton, modulus or gravitino,
undergoes flavor oscillation, and is thermalized due to the scatterings with
the ambient thermal plasma. We point out that the baryon asymmetry of our
universe can be generated due to the scatterings via the baryon number
violating operator. Our scenario can be tested in neutron-antineutron
oscillation experiments as well as other terrestrial experiments.