I want to try out low temperature cooking of some meat, e.g. beef  I don't have a reliable oven and am looking for advice before starting. Or alternatives to ovens.  I heard some people use meat in vacuum sealed plastic bags that they cook in a pot of water, (easier to measure temperature?)  What are the timings for weight/temperature combinations?  What dis/advantages does low temperature cooking have compared to grilled?  Anything else I should now before trying out? 
Cooking in a water bath in vacuum sealed bags is called sous vide.   The advantages include:   all of the meat is cooked to the desired temperature, and no higher, so you get 'perfect' doneness. The fibres of he meat don't contract due to the high temperatures and squeeze out the moisture, so the meat stays very tender if you have the right setup, you can put it on an leave it you can include flavourings in the vacuum bag so your meat steeps in the flavouring whilst it cooks.   Disadvantages include:   it can be expensive to set up (though not always, as work arounds exist) it can be difficult to keep at a constant temperature if you don't have an expensive set up the meat does not have any outer crust (although this is easily remedied after the cooking) takes a lot longer to cook.   I think it will be difficult to do in an oven as it is not often that ovens go as low as this type of cooking requires. 