I know that one of the guys at my LHBS does overninght mashing in his cooler...he wraps it in a sleeping bag, and puts it near the furnace and it only drops a couple of degrees overnight. I don't know about oven mashing and doing it...
Yea - see I'm was thinking of doing everything EXCEPT the boil. We have people coming over in the morning so the mini mashing would be a problem but if I can get all of that out of the way tonight . . . . and just start the boil tomorrow.
On my last batch, I did my partial mash the evening before. Collected the wort in a sanitized bucket fermenter, and put a lid on it. Boiled it the next day and didn't have any problems.
It would take quite a while for wild yeast or bacteria to build up harmful numbers/ruin the wort, and boiling it kills any of the few cells that might have gotten in there. You could boil it briefly and then tuck it in for the night, but don't think it would be necessary.