Here is an excerpt from the Star-K discussion:
All food must be fully cooked and placed in the oven before Shabbos. No food (cooked or non-cooked) may be placed in the oven on Shabbos to re-warm or cook. This is true regarding ovens, as well as warming drawers.
It is the opinion of Rabbi Heinemann that on Shabbos, for a thermostatically controlled oven that is running (as opposed to one shut off by timed bake), the door may be opened once at any time and all the food removed at that time. The oven may not be used any further for that Shabbos.
(btw, Itche, my oven also has a 12 hour cutoff. I turned it off so that I can leave the oven on over a Yom Tov.)