In this study, coupled bromate-oscillators constructed by adding 1,4-cyclohexanedione (1,4-CHD) to the ferroin-catalyzed Belousov-Zhabotinsky reaction are investigated in a batch reactor under anaerobic conditions. Various complex behaviors such as sequential oscillations and bursting phenomena are observed. At low concentrations of ferroin or malonic acid (MA), the development of sequential oscillations is found to depend on the ratio of [1,4-CHD]/[ferroin] and [1,4-CHD]/[MA] rather than their absolute concentrations. As the concentration of MA or ferroin was increased gradually, however, the minimum 1,4-CHD concentration required to induce complex oscillations reaches a plateau. Perturbations by light illustrate that the first oscillatory window is governed by the ferroin-MA-BZ mechanism, whereas the 1,4-CHD-bromate oscillator plays a prominent role during the non-oscillatory evolution and the second oscillatory window. Our conclusion is further supported by numerical simulations in which sequential oscillations observed in experiments are qualitatively reproduced by a modified FKN mechanism.