As a player he was a versatile offensive option, able to play as an attacking midfielder or a second striker. He played most of his 14-year professional career with Barcelona, with relative impact, appearing for four other clubs.
Born in Sabadell, Barcelona, Catalonia, Óscar made his professional debut with FC Barcelona, his local team. Between 1992 and 1994 he played in five La Liga matches for Barça who were champions each year and, after a loan at fellow top division Albacete Balompié, he returned and was often used (with good results) in a variety of offensive roles: during the 1995–96 season he scored 10 league goals, the most in the squad, even though he only started 11 of his 28 appearances; Barcelona came out empty in silverware, however.
With his role gradually diminishing, Óscar joined Valencia CF for one season, finishing off with Barça neighbours RCD Espanyol (teaming up again with brother Roger, for three seasons) and UE Lleida and retiring in June 2005 at the age of 32. On 7 January 2001, whilst playing for the second club against CD Numancia, he was taken to hospital after swallowing his tongue; in the following summer, he nearly signed for West Ham United, but an eventual deal fell through after a one week's trial and he returned to Espanyol, with whom he never scored more than one goal per season, during four years.