Born in Porto Calvo, Alagoas, Willian José started his career at local CRB's youth setup, before joining Grêmio Barueri in 2008, aged 17. On 1 August 2009 he made his first team – and Série A – debut, coming on as a late substitute in a 2–1 loss at Botafogo.

Willian José scored his first goal as a professional on 17 January of the following year, netting his side's only in a 1–1 draw at Sertãozinho for the Campeonato Paulista championship. He scored six further times during the campaign, which ended in relegation.