Forest Green Rovers
On 12 November 2013, Pennock was appointed as the new manager of Conference Premier side Forest Green Rovers.[10] He led the club to a 10th-place finish at the end of the 2013–14 season.
In January 2015, he was linked with the vacant managerial role at Gillingham, however he issued a statement declaring his aim to remain at Forest Green.[11]
At the end of the 2014–15 season he led Forest Green to a record highest league finish of 5th in the Conference Premier, meaning that the club secured a place in the play-offs for the first time. Forest Green were knocked out in the semi-finals, losing 3–0 on aggregate against Bristol Rovers.[12]
On 4 September 2015, after leading Forest Green to seven straight wins in the renamed National League at the start of the 2015–16 season, he was named August Manager of the Month.[13] On 5 September 2015, he led the club to an eighth straight league win at the start of the season with victory at Chester – a National League record.[14] On 5 February 2016, he was named National League January Manager of the Month having guided Forest Green to six straight wins.[15]
Despite taking Forest Green to 2nd in the National League, which was another record highest finish, he was relieved of his duties on 27 April 2016, just one week before the play-offs, after a poor run of results that had failed to see his side win in seven games.[16]
In November 2016, he returned to Welling United after being appointed as a consultant to new manager Jamie Day, who had been his assistant at Forest Green.[17]