Stable temperature control is highly desirable for reflectivity studies of binary liquid mixtures. In this article we report on the construction of an oven that possesses good temperature stability (∼1 mK/day) and small transverse temperature gradients (<1 mK/cm). The oven has a horizontal geometry and can be used for either x-ray reflectometry or ellipsometry measurements from the liquid/vapor surfaces of such systems. Details of the oven design together with test results are provided.