Brazil thrashed Chile 6-1 to go through, while Uruguay humiliated hosts Venezuela 4-1 at the Pueblo Nuevo Stadium in San Cristobal.
Brazil, inspired by the competition's top scorer Robinho, ended the first half with a comfortable 3-0 score line, which resembled their group stage win against the Chileans.
Defender Juan opened the scoring after 14 minutes, Julio Baptista added the second in the 16th minute, and Robinho made it three four minutes later.
Six minutes into second half, the on-fire Robinho added the fourth, to register his fifth goal past Chile in the tournament.
Josue made it five in the 38th minute, and Vagner Love completed the drubbing five minutes from time after Humberto Suazo's consolation for Chile.
The Brazilians will face 14-time champions Uruguay in Maracaibo in the Copa semi-finals.
Uruguay were helped by a brace from Atletico Madrid new signing Diego Forlan to beat Venezuela, Pablo Garcia and Crisitian Rodriguez were also on the score sheet, while Juan Arango scored for the hosts.