The Portuguese Cycling Federation announced the line-up on Wednesday. Bruno Pires of Saxo Bank and Sergio Paulinho (RadioShack-Nissan) are the reserve riders.
Costa, 25, recently won the overall title in the Tour de Suisse, after winning the second stage. He has been with Movistar Team since 2009, and won a stage at the Tour de France in 2011.
Oliveira is with RadioShack-Nissan. He was 2011 national time trial champion and this season finished third overall in the Circuit de la Sarthe.
Cardoso (Caja Rural), won the opening stage of the Vuelta a Castilla y Leon this year. He has ridden professionally since 2005.
Portugal sent two riders to the Beijing Olympics in 2008. In Athens 2004, Paulinho won the silver medal in the road race.