Graham Lowe, director of performance rugby, said: "We are delighted that Rob will be working on honing the skills of our most promising young talent both within Scotland and among our Exiles.
"He will work alongside our national under-20 management and will play a crucial role both before and during the IRB Junior World Championship in Italy this June in which Scotland under-20 are in a pool alongside South Africa, England and Ireland."
Rob Moffat said: "I'm looking forward to working with Scotland under-20 coach Peter Wright and his management team as well as providing additional coaching experience to these quality players. I'll be doing everything I can to help them to improve."
Peter Wright said: "I'm really excited to have someone of Rob's experience involved with us in the under-20s. From the viewpoint of both players and management he'll add a huge amount of know-how from which we will all benefit."