Two play-offs following Stevenage's sixth-placed finish. Following a 3–0 aggregate victory over Accrington Stanley, Stevenage earned promotion to League One after a 1–0 win against Torquay United at Old Trafford on 28 May 2011, with Bostwick playing the whole match. Bostwick started in Stevenage's first ever League One fixture, a 0–0 draw against Exeter City on 6 August 2011. Three days after the draw, on 9 August, Bostwick scored his first goal of the campaign in a 4–3 extra-time defeat to Championship team Peterborough United on 9 August 2011, scoring with a 25-yard shot that took the match to extra time. Bostwick signed a two-year contract extension with the club on 26 August 2011. He scored his second goal of the 2011–12 season in Stevenage's 5–1 home win over Sheffield Wednesday, with his 25-yard half-volley rebounding off of the post and into the net to give Stevenage a three-goal lead in the first-half. He played regularly during the season, making 53 appearances and scoring eight goals from midfield, as Stevenage lost 1–0 over two legs in the League One play-off semi-final. During his four seasons with the club, Bostwick made 207 appearances, scoring 22 goals. Peterborough United Bostwick signed for Championship club Peterborough United on a three-year contract on 9 July 2012, for an undisclosed fee. Peterborough chairman Darragh MacAnthony stated that Bostwick was manager Darren Ferguson's "number one transfer target for the summer". He made his Peterborough debut in the club's first match of the 2012–13 season, playing the whole match in a 4–0 home victory over Southend United in the League Cup on 14 August 2012. Bostwick scored his first goal for the club in his fourth appearance, halving the deficit with a "stunning volley from the edge of the area" as Peterborough lost 2–1 at home to Leeds United on 25 August 2012. He was made captain ahead of Peterborough's home match against Derby County on 27 October 2012, and opened the scoring in the match with a volley, his second goal of the season, in a 3–0 victory. Bostwick made 42 appearances for Peterborough in his first season there, scoring five goals, as Peterborough were relegated from the Championship. During the 2013–14 season, Bostwick reverted from central midfield to playing regularly at centre-back. He made 57 appearances in all competitions, scoring four times. This included six appearances in the Football League Trophy as Peterborough won the