The Portugal striker had been in good form this season.
The Portuguese star, who has become something of a cult hero during his time at the club, is struggling with a groin injury. It was confirmed by recently sacked boss Dougie Freedman to BBC Nottingham Sport after the recent 3-0 loss to Sheffield Wednesday that Oliveira looked likely to miss the rest of the season.
Now it is being reported in Portugal that the injury has also cost him a place at Euro 2016.
TSF Radio Noticias is reporting that the groin injury is worse than feared and that Oliveira was definitely out of contention for the Euros.
His form at Forest had seen him move into contention for the tournament after a recent international absence. He was due a call-up for the upcoming friendly matches with Bulgaria and Belgium. Instead he is back at parent club Benfica receiving treatment and will not be considered for the summer.
Oliveira spoke of his Euro 2016 desire earlier in the season, telling Correio da Manha:
"I want to go to the Euros. The coach is under observation phase and I want to enjoy it. Now I have a good opportunity to demonstrate my value."
The striker has been in fantastic form for Nottingham Forest this season. He has scored nine goals in 29 games for the club in an excellent season at the City Ground and will be fondly remembered by Forest fans.