Wicket keeper Cater has been with Oxfordshire since 2011 and has served as captain for the past decade.
He led Oxfordshire across all three formats within National Counties Cricket Association (NCCA) competitions for eight seasons.
After retiring from red ball cricket at the end of the 2022 season, he has continued to lead Oxfordshire for the past two years across both white ball formats.
Cater said: “It’s been a pleasure representing Oxfordshire CCC over the past 14 seasons.
“When starting back in 2011, I could never have imagined representing this county for so long.
“I will walk away with some unbelievable memories, across all formats.”
This included six centuries and 23 half-centuries, with his highest score being 117 not out against Shropshire in 2014.
He also completed 136 dismissals with the gloves, including 113 catches and 23 stumpings, and captained Oxfordshire to the NCCA Championship title in 2021.
In white ball cricket, he lifted the NCCA Twenty20 for the first time in Oxfordshire history in 2022.
He made more than 100 appearances across the Twenty20 and One Day Trophy format, amassing 2,829 runs at an average of 37.07, and became the first batter in NCCA history to score 1,000 runs in NCCA Twenty20 competitions during his final season.
Cater said: “Personally, scoring back-to-back hundreds down in Cornwall to get capped, and becoming the first NCCA player to score 1,000 Twenty20 runs are achievements I will look back on and be incredibly proud of.
“I want to say a huge thank you to all the players who have represented Oxfordshire CCC since becoming captain.
“Without your hard work and dedication, the success the county achieved would never have been possible.
“I believe more trophy success is just around the corner, and I will be supporting from afar and hope the boys can achieve this very soon.”
County men’s head coach, Rupert Evans, added: “During his 14 years playing for Oxfordshire, Jonny worked hard to develop his batting and wicket keeping skills to become one of the best wicket keeper batters in National Counties Cricket.
“He was a tough, competitive captain who enjoyed being in a battle. His style of captaincy did not always endear him to the opposition, but it gained him respect from our players, opposition teams, and officials.
“Jonny, you have been a wonderful servant to Oxfordshire Cricket.”