Bicester Town Council will get five new members from 2015, it was agreed on Monday night.
Cherwell District Council (CDC) approved plans to increase Bicester Town Council from 15 members to 20, and to move certain areas of land in the parishes of Bucknell, Caversfield and Chesterton into the town council’s area of responsibility.
Changes were approved ahead of a district boundary review later this year.
CDC leader, Councillor Barry Wood, said it had been, “...the culmination of a substantive piece of work” as he introduced the boundary changes.
Under the changes, some land in Blackthorn will become part of the parish of Ambrosden from 2016.
From 2015, Chesterton Parish Council will increase from six members to seven, and Middleton Stoney Parish Council will increase from five to seven.
Piddington Parish Council is also due to increase from five to seven members in 2016.
No changes were proposed for Upper Heyford, as the size and composition of the parish is likely to change over coming months as a result of major planning applications, including the Heyford Park development.
Councillor James Macnamara, ward member for the Astons and Heyfords, said: “There will be two different communities with two very different outlooks and background that will have to be represented by one organisation.”
He asked officers to keep the situation under close review.
Cllr Wood said the council would help Heyford Park Residents’ Association so it could become, “a de facto parish council in waiting.”