What is the blessing on oatmeal mixed in hot water?

Hello,

If you cooked it in water, the blessing is mezonot. However, if you soaked it in hot water in a secondary vessel until it softened—and they did not stick together—the blessing is ha'adamah. If they did stick together, the blessing is mezonot.

Sources: See Shulchan Aruch (Siman 168, Sif 2), Mishnah Berurah there, and Sefer V'Zot HaBerachah (pages 104-105).

Regards,

Hillel Meirs.