A RPO is a run-pass option, which is mostly utilized by Shotgun-based Spread Offenses; however, this concept is utilized by some Triple Option colleges this spring.
The Quarterback opens at 90 degrees, runs to the tackle, and throws the ball to the streaking Playside Receiver UNLESS the Corner stays over the top of the Receiver.
IF SO, the Quarterback runs the two-way option with him and the Backside A-Back versus #2. The Quarterback turns up off the Playside Tackle and scores UNLESS #2 steps at the Quarterback. If so, the Quarterback parallel pitches to the Backside A-Back.
The Playside A blocks the Safety.
The Playside Tackle and Guard double team #1 (defender covering the playside Tackle).
The Center/Backside Guard/Backside Tackle slides to the playside (they cannot go upfield) as they would in pass protection.
The Backside Receiver cuts off the Backside Corner.
The B-Back runs his zone path, which is through the outside leg of the tackle, and blocks the Mike.
Here is the Zone Option RPO in action versus the 4-3 defense: