We had the same situation a few years ago.  Landowner needed horse pasture.  At the time, our bean chem program was Treflan and Sencor.  After the beans were out, we worked the ground a few times and sowed the grass.  We got at best a half of a stand.  We did a re-seed in the spring, but he may have overgrazed it after that, and it was never as good as it could have been.