Stephen showed early promise during his time at Essex, scoring 110 on his debut against Cambridge UCCE in 1996 and was picked for the England U19 team that won the World Cup, Peters helped them to this by scoring a century and getting the man of the match award in the final. Stephen then moved to Worcestershire to regenerate his career. After three seasons at Worcester, he moved to Northants for the start of the 2006 season. While at Northants, he scored his then highest first class score when he made 178* against his former club Essex in his first season. On 1 September 2009, Stephen alongside David Willey signed a two-year contract extension keeping them at the club until the end of the 2011 season. The 2010 season was his best with the bat as he twice set himself a new highest first class score both coming against Middlesex, making 183* against at Northampton on 24 April and then falling one short of his double century at Lord's on the 6 June. In January 2012 it was announced that Peters will train in Sri Lanka with teammates Ben Howgego and David Murphy courtesy of Northants' overseas player Chaminda Vaas.