The 22-year-old has played seven times for Manchester United's first team and scored two goals since joining in August 2010, but he is yet to feature for the Reds this season having spent much of the campaign training and playing for the Under-21s.
With competition for places in attack particularly fierce in Sir Alex’s senior squad, the United manager feels it’s best for Bebe to gain experience elsewhere for the time being.
“We feel the boy has got to get good experience at a better level than our reserve team,” Sir Alex told MUTV.
“He’s gone to Rio Ave who are fifth in the Portuguese league at the moment – they have a young coach [Nuno] who has a very good reputation.
“Bebe has done quite well in the last two or three months. He got a cruciate knee injury when he was on loan in Turkey last season and that derailed him for a bit. Coming back from these injuries takes time but he’s started to develop quite well.
"Hopefully his spell in Portugal, where he is from anyway, could help him.”