Is it possible to cook on a BBQ that was previously used for non-kosher food such as BBQ’s at parks and campsites? Also, can an outdoor gas or charcoal grill be kashered?

Since food is roasted directly on the grill, the grate must be heated until it glows (libun gomur) to be properly kashered. This can be done either with a blowtorch (which should only be used by qualified and experienced individuals) or by sandwiching the grates between charcoal briquettes and setting them on fire. In addition, if the grill has a hood, the empty gas grill cavity must be kashered by cleaning, closing the hood and setting it to the highest setting for one hour (libun kal).  Alternatively, one may replace the grates and kasher only the grill cavity as explained above.