Run the oven at about 150 for a while - so that the metalwork can expand slightly - then as soon as you feel confident use a damp cloth to grip the glass cover.
Unscrew Anticlockwise
Good luck...
Peccavi
February 2011
heat it up with a hair dryer,then use a dry cloth to remove or rubber gloves
mm
February 2011
I can answer this question...
How can I undo a jammed glass cover over oven light bulb?