Before somebody destroys their work, lungs, or home... I should probably address a few issues:
It's super important to keep the oven on it's lowest setting. Do not use 'broil', and don't go above 250° or so. The flashpoint of paper (The temperature at which it combusts) is 451°F. So keeping it 200° below that point is fairly safe.
There are also several things I would avoid...
1. Do NOT put a painting in the oven that is dripping wet with solvents.
It WILL combust, or at the very least create some pretty noxious fumes. This particular painting had been sitting around for weeks, so any solvent on the surface was long gone. I was simply facilitating the oxidation of the oils... not burning off stuff I didn't want.
2. Do not do this with non-maleable surfaces. Pretty much anything you put in there will warp at least a little (like a cookie sheet). Things like wood will especially warp, and you will be unable to flatten them out (like Arnie mentioned). Because I paint on Strathmore 500 Series illustration board (which is just thick paper), I can always wet the back of the painting and let it relax for a few days afterward.
3. Also remember that many woods (like MDF) are synthetic, filled with glue, or may be pressure treated. Do not put these in the oven, they are likely to release chemicals, lose their longevity, and in the case of pressure treated wood... kill you.
Some other stuff to keep in mind:
The toxicity of oil paints lies in the solvents, and the heavy metals in the pigment. When you bake the painting the metals are not becoming airborne, so it's relatively safe. Aside from the solvent issue (which I mentioned), the only thing you'll notice is a possible burnt oil smell when you open the oven (like an old grease fire). It's not pleasant, but not deadly either.
Also, I only do this for 5 or 10 minutes at a time. Give it a chance to slowly cool, and if it still needs it, pop it back in for another 5. Keep in mind that oils do not dry through evaporation like acrylics do. Rather, they dry through oxidation. Heat helps this process, but so does cooling. When you remove the painting from the oven, it may not feel dry. But give it time to cool, and you'll find it dries rapidly.