If you want to weigh the grains dry (the same amount as any other hot cereal) and then cook it afterwards in liquid, that would be fine. Alternatively, you could cook up a big pot for the week and then weigh it after it’s already cooked.
For weight loss: 1 oz. dry breakfast cereal = 4 oz. cooked grain.
For maintenance: 1.5 oz. or 2 oz. dry breakfast cereal = 6 oz. or 8 oz. cooked grain.