Do foods with water exceed 100° celsius in the oven? I was thinking that water in liquid state can't normally be much above 100 degrees celsius because it boils, so probably foods with lots of water like vegetables don't warm more than 100 degrees. Does this make sense? Suppose the oven is set at 200 degrees for example.
 A: In the absence of added water to the food the temperature of food will not be uniform and can rise above the boiling point of water and most cooking is finished when the internal temperature of the food is below the boiling point of water.  With the added water the temperature is dictated by the temperature of the boiling water which can be elevated to up to about $120 ^\circ \rmC$ but adding salt only increases the boiling point by a few tenths of degrees.
In a conventional oven the rate at which heat is transported into the food depends on the temperature difference between the food the temperature of the oven.
The latent heat of vapourization of water is quite large.  
Assume that the water is present just in the food.
The temperature of the food will rise with its outside temperature greater than that of the inside.
The water in the food is converted into vapour at the surface first and then deeper down in the food.
This evaporation slows down the rise in temperature but the food can reach temperatures above the boiling point of water because parts of the food will then contain water vapour rather than liquid water.  
An example of the slowing down of the rate of temperature rise is the BBQ stall.
When meat is cooked in a BBQ its temperature steadily rises and then dwells for a time at about $70^\circ \rm C \; /\; 160 ^\circ \rm F$ and the temperature then starts rising again.  The explanation of this is that during the stall the rate at which heat enters the meat is equal to the rate at which heat is used to evaporate water from the meat and hence the temperature of the meat does  not rise.
Too rapid a rate of evaporation can be a problem and so food liked baked potatoes and baked apples is often cooked in foil to reduce the rate of evaporation.  In such cases the temperature of the food rises more rapidly.
A: To give a more complete answer to your specific question, the boiling point is when the molecules in water have enough energy to "escape" the liquid and become gaseous. When water boils in a pot the temperature will be 100C, which is measured by the average kinetic energy of the water molecules. The molecules that "break free" will be the ones that have the most energy at any given time. So as the more energetic molecules escape they take a disproportionate amount of energy with them causing the average energy of the boiling water to decrease. This prevents the specific situation that you are describing.
There is also the phenomenon of super-heated waterwhich is not what you are describing but is a way to raise liquid water to higher than boiling point temperatures.
