Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3 - δ (BSCF) is an interesting material for high temperature oxygen permeation membranes and solid oxide fuel cell cathodes, applications for which oxygen transport properties are crucial. Here oxygen isotope exchange is performed on dense BSCF films prepared by pulsed laser deposition on MgO single crystal substrates. The oxygen isotope profile is analyzed by secondary ion mass spectrometry to extract tracer diffusion coefficients D∗ and effective surface exchange constants k∗. Tracer diffusion has a low activation energy of 0.5 eV. At moderate temperatures, the related oxygen vacancy diffusion coefficient DVÖ is significantly larger than that for (La,Sr)(Fe,Co)O3−δ perovskites.