Working with simulations, testing and validating theories often requires a large number of simulation runs. The discrete event simulation environment OMNeT++ already provides functionality for distributed computing, yet the simulated model and modules to be parallelized have to be declared manually. Apple Mac OS X comes with Xgrid support, which allows easily setting up an ad hoc grid for parallel computing. In this paper we will describe the features we had to add to OMNeT++ to be able to use Xgrid to parallelize even several thousand runs. We will point out how to use Xgrid to distribute runs of a simulation not only to multiple CPU cores but also to multiple machines without modifying the simulation itself. Our analysis will reveal that Xgrid allows to reduce the computing time almost proportional to the added parallel computing power.