Sanchez would make both goals of the victory against the great rival, CSD Municipal in the second round of the Central American zone and in the return his team ended up tied to zero.
In the third round of Central America (end of the zone), Oscar in the first game scored the winning goal against Deportivo Saprissa of Costa Rica at minute 2 of the game and in the lap played in Guatemala he was again the figure of the match by remarking two goals at minutes 14th and 31st that would mean the classification of Comunicaciones and subsequently the consecration of the "crema" team of the CONCACAF 1978 Champions' Cup.
In a friendly match played at the Estadio Mateo Flores, Sánchez scored the only goal of the victory of his team Comunicaciones to Dinamo Zagreb of Croatia.
After his departure from Comunicaciones, Sánchez played for the clubs Municipal, Aurora F.C., Cobán, CD FAS de El Salvador and Tipografía Nacional; He retired in 1992, after having scored 320 goals in all competitions.
His full international debut occurred on September 26, 1976, at a 1978 World Cup qualification match against Panama, where he scored a hat-trick on a 7–0 win.