The application of a deformable grating to the realization of a time delay compensated monochromator is presented. The grating is realized as a replica on a thin glass substrate and the deformation is realized with a mechanical bender. The monochromator is conceived for the spectral selection of a single harmonic in the spectral range 20-80 nm in beamlines exploiting the high harmonic generation process. A possible optical design requiring only two deformable gratings, a mirror and an intermediate slit is presented.