Bonsor played in the 1872 FA Cup Final - the first ever final in the FA Cup's history - and finished on the winning side. He played for the Wanderers that day, and with Wanderers he won the cup the following year as well.
Bonsor appeared in the 1875 final playing for Old Etonians, scoring a goal, as his side drew 1-1. They lost the replay, but Bonsor was back in the final the following year. He played for Old Etonians again, and scored again. Old Etonians drew that match 1-1 but, once again, lost the replay.