The 30-year-old returned to Glasgow Warriors in 2013, having enjoyed a two-year stint with Sale Sharks, but he has decided to leave Scotstoun for the second time in his career.
Vernon offers versatility and has represented Scotland as both a forward and a back but his career has stalled over the last few years due to injuries.
After falling down the pecking order with Warriors, Vernon has agreed a switch south of the border to English Championship outfit London Scottish, and he insists it was too good an opportunity to pass up.
Vernon said: "I'm really excited to join London Scottish.
"I enjoyed hearing the vision that the management have for the club and was immediately convinced it was the right move. This unique opportunity was too good to pass up."