You really want the oxtail cut up and packaged for you, it's a batsrad of a job to strip one down - the recipes will assume that you have tail in this form anyway.

Re the cooking beef in the sun - good quality beef really benefits from slow cooking processes, and the final temperatures required are relatively low compared to most other meats:-

Cooked Temperature Range Description
Blue (46 – 52?C) Blood-red meat, soft, very juicy
Rare (52 – 54?C) Red center, gray surface, soft, juicy
Medium Rare (54 – 60?C) Pink center, gray-brown surface
Medium (60 – 66?C) Slightly pink center, becomes gray-brown towards surface
Medium Well (66 – 71?C) Mostly gray center, firm texture.
Well done >160?F (>71?C) Gray-brown throughout.

So instead of blasting your beef with 180?C air in a hot oven for a short period of time to bring it up to the required temperature you can apply a gentler heat source for a longer period of time - we regularly cook a roast joint of beef for 6 or more hours with the oven set on minimum with the door ajar in order to get an oven temp of around 80?C - the Australian sun on hot summers day will quite happily bring a covered roasting pan up to this sort of temp.