How to repair a large hole in OSB?
Turn off the power feeding that outlet and move the wires out of the way.  Set the blade on your circular saw to make a cut just a little bit deeper than the OSB is thick.  From the opposite side of the wall than what is shown in the picture, cut a rectangle out of the OSB that includes the top and bottom of the hole and extends to the middle of each stud to either side.  Cut a piece of OSB to fit the hole, and screw it into the studs.  

Alternatively, if you don't want to see a patch, you can just take off the whole piece of damaged OSB and replace it with a new one.