competition; Bostwick played the whole match in the Final, a 3–1 victory against Chesterfield at Wembley Stadium on 30 March 2014. He signed a new three-and-a-half year contract with Peterborough on 10 March 2015, with MacAnthony stating Bostwick could return to his midfield role as "you can see what he brings to that position". He scored seven times in 41 matches throughout the 2014–15 season, which included ending the season scoring three times in his last two games. Having played regularly in the first-team under Ferguson for two seasons, Bostwick continued to do so under new manager Graham Westley during the 2015–16 season, who had previously managed Bostwick at Rushden & Diamonds and Stevenage. He played 43 times and scored four goals that season, with Peterborough finishing in 13th place in League One. Bostwick scored three times in 45 appearances under the management of Grant McCann throughout the 2016–17 season and was voted as Peterborough's Player of the Year for the season at the club's end-of-season awards ceremony. During his five years at Peterborough, he made 228 appearances in all competitions, scoring 23 times. Lincoln City Bostwick signed for newly promoted League Two club Lincoln City on a two-year contract on 20 July 2017. He joined Lincoln for an undisclosed fee, with Peterborough having received a higher offer from Blackburn Rovers, although Bostwick did not want to relocate to the north of England. He made his debut for Lincoln in the club's 2–2 draw away at Wycombe Wanderers on 5 August 2017, and scored his first goal in a 2–1 victory against Chesterfield at Sincil Bank on 7 October 2017. He made seven appearances in Lincoln's EFL Trophy campaign that season as the club won the trophy after defeating Shrewsbury Town in the 2018 EFL Trophy Final at Wembley Stadium on 8 April 2018. It was the second time Bostwick had won the trophy in his career; and the fourth cup competition he had won at Wembley Stadium. He scored six times in 51 appearances during his first season at Lincoln and was selected in the 2017–18 EFL League Two Team of the Season having helped the defence keep 17 clean sheets. Bostwick extended his contract with Lincoln for an extra year on 26 April 2018, keeping him at the club until June 2020. During the 2018–19 season, Bostwick scored in Lincoln's FA Cup third round 2–1 defeat to Premier