The 20-year-old attacking midfielder, who signed from non-league side FC United of Manchester in January of last year, has made three starts and come off the bench seven times since making his debut in October.
Simoes – who was born in Portugal and spent time in Benfica’s academy – scored his first professional goal in the 2-1 loss at Derby County in January.
Head coach Gerhard Struber told the club's website: “Elliot has really impressed me since I arrived. He is a big talent but what is really important is his energy, desire and work ethic. I am convinced that not only will Elliot be a big player for us in the next games, but also the next years.”
Simoes said: “It’s been a good year since I’ve been at the club, and the club has really taken care of me – all the staff, every player – as I’m one of the younger players, because it was a big step up from where I came from. I had to get used to the environment and the football; it’s been really helpful and it just shows that they’ve got a lot of faith in me and believe I’ll do well.”