There was originally an admission charge for the game at Municipal de Lagos Stadium, Tapada de Sao Joao, 8600 in Lagos, Portugal, but that has now been scrapped and admission will be free.
Posh are due to return to the UK the following day. The game against Orient means a quick reunion with his old club for summer Posh signing Hector Kypriano.
Posh failed to arrange a friendly against a local team while they are away.
They have added another friendly to their schedule though. They will travel to National League Barnet on Saturday, July 16.
The first Posh friendly after their return is at Steve Evans’ Stevenage on Wednesday, July 13.
Revised friendly schedule: July 8 Leyton Orient (in Portugal), July 13 Stevenage (A) 7:30pm, July 16 - Barnet (A) 3pm, July 19 Luton (H) 7:45pm and Kings Lynn (A) 7:30pm, July 23 - Hull (H) 4pm and Scunthorpe (A) 3pm.