We report on a discrete layer-by-layer magnetic switching in Fe=MgO superlattices driven by anantiferromagnetic interlayer exchange coupling. The strong interlayer coupling is mediated by tunnelingthrough MgO layers with thicknesses up to at least 1.8 nm, and the coupling strength varies with MgOthickness. Furthermore, the competition between the interlayer coupling and magnetocrystalline anisotropystabilizes both 90° and 180° periodic alignment of adjacent layers throughout the entire superlattice. Thetunable layer-by-layer switching, coupled with the giant tunneling magnetoresistance of Fe=MgO=Fejunctions, is an appealing combination for three-dimensional spintronic memories and logic devices.