The 18-year-old forward has linked up with Boro under-23s and started in the 1-0 Premier League Cup win over Queens Park Rangers on Monday.
Gyimah-Bio, having starred to Posh in their FA Youth Cup last season, has previously been tracked by a number of Premier League clubs and Bundesliga side Wolfsburg.
The duration of his trial period is currently not known, although he is expected to feature for Graham Lee’s side against Stoke City next week.
Gyimah-Bio signed for Posh when he was aged 15 and is born to Ghanian parents.
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