i know what you mean, my mother in law has a streak there too. check your owners manual.

its easy for the grease to get in on mine, and my m-in-l's, as the two pieces of glass arent a single unit, one is mounted over the other, and something spilled on the top edge of the oven door can drip in. def. a design failure.

I just cleaned my GE double convection oven. it is fairly easy to separate the two sections but you will need both a philips head screwdriver and a Torx driver to do it. Pull the oven door off and lay it down, inside up, on a table padded with newspapers. Be advised: These doors are HEAVY!! Once down, inspect both the outer edge and the interior outer edge that is up to see the screws (5 outer and 4 inner on my GE) you have to remove. Do so carefully and the two pieces will then come apart. Have a safe, flat place ready to put the interior piece. Now you can see the glasses, of which there were 3 on my GE. You may also see a layer of greasy crap on the bottom of the units, which should be cleaned first.

Try glass cleaner first, if that does not do it, get a jug of GoJo Orange Hand Cleaner at probably any hardware, auto parts store or Costco. This is the stuff that will easily remove the black grime from an auto mechanics hands and it is amazing for kitchen grease also. Just rub it in, wipe it off, repeat and follow with glass cleaner to shine it up. It also works on the porcelain surround.

Be very careful and meticulous when you reinstall the door as some, like my GE, are not fun to install and if you do it wrong it can fall off and hurt you!!! Be careful.