text: The 28-year-old Scotland international has spent the last two seasons with Wasps, having previously had a six-year spell with Glasgow Warriors.
  "His style fits the way we play perfectly and he will provide excellent competition," said incoming Quins director of rugby John Kingston.
  "We are looking forward to adding his expertise next season."
  Harlequins have not disclosed the length of Jackson's deal at The Stoop.
  Jackson has won 28 caps for Scotland since making his Test debut against New Zealand in 2010, and made one appearance at this year's Six Nations.
  "I'm extremely excited to be starting a new challenge with Harlequins," he said.
  "After speaking to John Kingston and Conor O'Shea I could see how great a club it is."
  Kingston will replace O'Shea in charge of the south-west London club this summer, with O'Shea leaving the club to take charge of Italy.
target: Harlequins have agreed to sign fly-half Ruaridh Jackson from Premiership rivals Wasps ahead of next season.