We cut our larger grasses down yesterday evening to about 7". I'm not sure about the smaller grasses but I would think if there is not any new growth (or very little) that it would not hurt. In fact, I think I'll chop on my little fescue too (I usually don't) and see what happens!

I plan to cut back my grasses in the next week. It is raining right now. I do exactly like gersch says, my larger grasses I cut back to about 7 ". My small grasses to about 3-4". It is kind of proportional to the size of the plant.

I would NOT recommend cutting completely to the ground level. I did that one year and the grass struggled to come back.