Have no idea what Sous-vide cooking is? It is simply put, a method of cooking using a water bath to bring food to exactly the right temperature (used in many high end resterants) thus preventing overcooking and in many cases, toughening the food being cooked. (Scallops come to mind)

Given the fact that many homebrewers use a cooler to mash grains in because of the excellent thermal properties and ability to maintain a temperature for relatively long periods of time, it is a logical step that a cooler can be used as a cooking device in the same way it is used as a mash tun, heat water to a bit over the desired temp of the finished food, put food in vacuum bags and seal up, add to the hot water and let it rest for a half hour, hour, whatever!

I have done this with cheap steaks that always seem to come out tough and chewy on the grill, I season them as I like, put them in vacuum bags, vacuum just long enough to get the air out and seal em up.

Next I get the water heated to 155, and into the cooler it goes, when the steaks are added I check that the water is dropped to 145-146 degrees (rare steak)I close the cooler lid and start prepping everything else for dinner, after 45 minutes or so I pull em out and get the grill blazing hot, I sear the steaks to desired final doneness of the guest, rare just gets a quick sear on both sides, medium or well get a longer searing.

This can be done with steak, chicken, fish, whatever you like that can be brought to desired internal temp within the time your cooler can hold temp.

I really like this method for big events as I can have everything ready to roll, the steaks are cooked already and cannot overcook because of the set temperature, they just need a quick char to finish em off, less time spent cooking when guests arrive and the steaks are tender and juicy because the connective tissues gelatinize instead of toughening up.