 He also spent two years in Greece, with Olympiacos.Born in Salamanca, León, Óscar began his career with Real Valladolid, making his first-team – and La Liga – debut in the 1–0 home win over UD Las Palmas on 7 October 2001, one month shy of his 19th birthday.Establishing himself as a regular by the start of the 2002–03 season, he was the side's best scorer in the following year at 10, in spite of a final relegation.