Acetone, methylmalonic acid, malonic acid, iodomalonic acid, and phenylmalonic acid are compared under identical conditions in the Briggs-Rauscher oscillating System. Each of these five substrates consumes iodine to form an iodo product and produces iodide at the same time. The rates of iodine consumption have been measured for each of the substrates individually. To a first approximation, all of the substrates behave in a similar manner when compared at concentrations which react with iodine at similar rates. A skeleton model for the oscillatory system cannot quantitatively-predict variations of the oscillatory period with concentration for any one of the substrates. Several reactions and processes are discussed which must be part of a complete description of the oscillator but which make only;marginal improvements when compared to the skeleton model : reduction of iodate ion and iodine by hydroperoxy radical, reduction of iodate by the substrate enol, second-order reduction of iodate by iodide, net oxidation of iodine by hydrogen peroxide, continuous HOIO production, and decomposition of the iodo products.