Temperature is the measure of thermal energy, or the movement of molecules that make up an object. It describes how fast the atoms and molecules that make up the object are moving.
Temperature is related to mass because objects with more mass change temperature more slowly than objects with less mass. The oatmeal in each bowl has a different mass. The oatmeal with the most mass (Bowl #3, with 1½ packets) has to lose the most heat for its temperature to fall. It takes more time for the object with more mass to cool than the same object with less mass.
Imagine both a glass of water and the ocean are the same temperature. It would take a lot more heat loss – and a lot more time – for the ocean to cool by 1 degree than it would take for the glass of water to cool by 1 degree.