You need three receivers and the QB. You can use four if you like.
The QB sets up on the minus thirty yard line. The three receivers can set up anywhere from 15 to 30 yards away from the QB. One receiver five yards from the left boundary .....one receiver in the middle...and the other receiver five yards from the right boundary.
The coach stands behind the QB and give the QB a command.....3 step.....5 step .....7 step....roll out......the QB takes the drop barked out by the coach .......then he starts to look from one side of the field to the other waiting to see which of his receivers raises his hand. The coach will point to the receiver that he wants to raise his hand to signal to the QB that he is the open receiver. In the next progression the coach then requires the QB to look for the receiver that is raising both hands...........The coach tells all the receivers to raise one hand whenever he wants......and to raise both hands whenever the coach points to him. It is up to the QB to look for the open man.
The drill should last no more than 5 seconds. The coach needs to point to a receiver quickly within that time frame. He is looking at the QB insuring that he is acquiring a complete look all the way across the field. At first the QB will not find the raised hand. Be patient. with time he will identify it more quickly. Insist that the QB be mechanically correct. (identify turn step toward the target release the ball.)
Look for the QB to have " nervous feet" Settle him down and insist that he throw off of the correct foot. After some repetitions with one hand then have the receivers all raising one hand. Point to the one that you want to raise both hands. Time is of the essence. Now the QB must look more closely. The time for release of the ball should eventually be three to three and a half seconds. Good Luck.
This drill will help the QB have a greater field of vision. It will inculcate the need to find the open man or as we say find the touchdown. He is obligated to look all the way across the field. His reading skills will improve......his throwing skill from an off balance posture will improve...he will effectuate a better control over his mechanics. And finally he will appreciate the time concern and release the ball more quickly with practice.