Could be Timothy, but could also be Creeping Foxtail (Alopecurus arundinaceus):
http://commons.wikimedia.org/w...
http://biology.burke.washingto...
I have a hard time telling them apart until the seed heads mature. When the seeds are ripe, the individual spikelets of Creeping Foxtail easily come loose from the rest of the head (even a light breeze will blow them off) whereas the heads of Timothy stay largely intact.
