An experimental and theoretical description of the oscillatory electrocatalytic iodate reduction system in alkaline solution is presented. Experimental measurements suggested the crucial role of a negative differential resistance as well as the presence of hydrogen evolution in the oscillatory instability. A simple kinetic model with one chemical species was developed which involved: (i) an iodate reduction current with N-shaped potential dependence due to a Frumkin repulsion effect; and (ii) an additional 'iodate-independent' current providing process. The dynamical behavior of the model compares favorably with experiments as far as voltammetric profiles, stirring effects and bifurcations between stable and oscillatory states are concerned. It is further shown that the model can account for oscillatory states in a number of related electrocatalytic systems.