Osborne's 48th minute strike, off the inside of the post, sealed victory over Boston Town - in a match where United fielded 22 different players.
United were kept largely at bay by excellent goalkeeping from Town stopper Travis Portas, with Dan Mooney and Frankie Maguire both striking the woodwork in the second half too.
United (first half): Cameron Gregory, Cameron Green, Michael Bostwick, Keaton Ward, Martin Woods, Adam Marriott, Tony Weston, Jacob Scott, Ed Daffern, Trialist A, Trialist B.
United (second half): Jake Lovelace, Tom Leak, Jacob Hazel, Dan Mooney, Jordan Richards, Sam Osborne, Frankie Maguire, Zak Mills, Dylan Hill, Ellis Perry-Burdett, Trialist A (Oliver Wilson 62).
Referee: Aimee Keir.
Attendance: 450.
PIC: Lee Keuneke.