You've just killed literally thousands of kobolds, tsaoli or gibberlings and they left a litter of gold pieces along with their fallen corpses on the battlefield's ground. Youre faced with the arduous task of going one by one picking up whatever they've left behind.

Is there a quick key or command which will automatically collect everything in the vacinity like the newly released Dungeon Siege.

No.
The words "newly released" should have given you a clue already. ;)

Well... I admit that looting thousands of dead little "ankle biters" would be a daunting task. However, I have never come across more than about 50 dead little corpses in my various campaigns. And in those cases I simply pick up only the gold pieces and spell scrolls, and leave the other junk behind.