The zone read play has been done to death by pretty much every football-oriented blog out there, so we don't see a need to rehash it all from the beginning here. We'll just give the basic description and present you with some links for further reading. We did a piece on defending the zone read here, last season.
Very simply put, the OL on the backside veer blocks, which leaves the outermost defender totally unblocked. This is almost always the DE, but in principle it can be an OLB. The playside zone blocks. The QB reads that DE and decides whether to give the ball to the RB or take it himself depending on what the DE does. If the End crashes and takes the RB, he takes it. If the DE stands put, he gives it to the back, which makes the play just an inside zone. This is just the basic read that any QB makes in the triple option, like GT. Both Chad Morris and Gus Malzahn put a bubble screen on the backside of the zone read, as an added wrinkle for the defense, and Morris would like to run the inside zone tighter to the Center than Rich Rodriguez. His original zone read is described in the video above, but as defenses adapted, guys like Malzahn and Chip Kelly added the zone bubbles, H-back motion and blocking, and downfield attacks to keep the defenses honest.
See inside for instructive videos and links.
Here you see Oregon running the same thing, with the same motion we'll be using. The added wrinkle is that on occasion the blocking WR will go downfield and instead of cracking a safety, he'll be left wide open because the defense expected the ball to hit the bubble WR. Again below you'll see almost all the variations in Oregon's system, which is the same things you'll see in Death Valley.
So thats the zone read and zone bubble, and if you want to go deeper into the play and the added wrinkles, here are some links to explanations.
Varsity Blue - Rich Rodriguez's Zone read - notice what he says about reading the defense. Also, Morris does not block the backside End on the trap either.
Smart football Defending the ZR with the Scrape Exchange, Gun Triple Option, Urban Meyer's Zone read rules
Offensive Breakdown - Oregon Inside zone series
Spread Football - Midline and Zone read rules, this is good for the actual basic teaching of the play.