This paper applies vibrational feedback control to time lag systems. Averaging theory for differential delay systems is presented and then applied to aid in the design of periodic controllers. Both stabilization and transient issues are discussed. An illustrative example is given which demonstrates that the proposed controller : 1) provides superior robustness properties in comparison to time-invariant controllers when applied correctly; 2) is not robust with respect to ummodeled delays; and 3) does not have zero placement capabilities, in the sense defined in the paper.