Mrs J Westrope and Mrs S Evans have applied for outline planning permission to develop the garden of a bungalow off Grange Avenue.
They also want permission to demolish the bungalow and build a new one with three bedrooms.
The development would have 20 parking spaces.
Peppard Parish Council has opposed the application, arguing that this would not be an infill development and would be out of character with the area as well as negatively impacting neighbours.
It said: “The development sits behind the existing houses and forms a new complex and alignment of dwellings completely separate from any existing road layout or housing arrangement and therefore could not be said to comply with the spirit of infilling.
“The application site is situated on the edge of Rotherfield Peppard rather than within it.
“Although the applicant has drawn a line along the boundary of the site and the adjacent paddock, it is not following the building line and is enclosing two green spaces which do not have any residential use.”
More than a dozen residents have objected to the plans, raising concerns such as an increase in traffic and urbanisation of the Chilterns Area of Outstanding Natural Beauty.
Leslie and Linda Conway, of Grange Avenue, said the development would more than double the number of homes in the street and would be “overbearing”.
Ian Heriot, of Church Lane, said the application should be regarded as “Trojan horse” for more development in the future.
Diana Greenfield, of Grange Avenue, called the plans “unacceptable over-development of a rural location by garden grabbing”.
Planning agent Bell Cornwell said: “The proposed development would comprise an infill development that would be within a residential area and it would not result in the existing settlement being extended or altered.
“The proposal would not give rise to overlooking nor loss of privacy.”
South Oxfordshire District Council was due to make a decision this week.