I saute mushrooms for my veggie a LOT. Should I eat a cup of raw and then cook, or cook and then measure a cup? They cook down quite a bit!
I always measure my veggies in the state I'm planning to eat them in. If I'm eating them raw, I measure them raw. If I'm eating them cooked, I measure them cooked. I have no idea if this is correct or not, but it's worked for me.
There are vanishingly few vegetables that I would stress about measuring calories for.
Those that are higher calorie, it's easy to look up calorie counts by prep method.
My coach says to measure raw always.
According to the Ideal Protein protocol, everything should be measured pre-cooked, including meat.