Place the red wine in a small pan and crumble in the beef stock cube. Bring to a boil, reduce the heat and simmer until reduced in volume by a third.
Add the onion and the pheasant legs and simmer gently for 15 minutes or until the pheasant legs are cooked through and tender and the sauce has reduced to a thick consistency. Season, to taste, with salt and freshly ground black pepper.
Place the pheasant legs onto a warm serving plate and spoon over the red wine sauce and the onions. Garnish with the fresh thyme and serve at once.