The influence of oxygen in Belousov-Zhabotinsky systems with substituted malonic acid derivatives RMA (R = H, Me, Et, Bu, phenyl, and benzyl) has been studied. A significant influence of oxygen and organic substrate has also been found for the autocatalytic oxidation of the catalyst by bromate. In both the presence and the absence of RMA, oxygen always increases inflection times of the autocatalysis when compared with anaerobic conditions (argon bubbling). In general, period lengths P of RMA-BZ systems increase with increasing Taft sigma* constants of substitutent R and a linear log P - sigma* relationship has been found. In aerobic conditions (oxygen bubbling) the MA-BZ system is an exception because malonic acid (MA) BZ period lengths are, at these conditions, significantly lower and deviate from the linear log P - sigma* relationship. The deviation appears to be related to the increased release of bromide ion when MA-BZ systems come in contact with oxygen. Model computations indicate that the decrease in inflection time of the autocatalysis is related to the scavenging of BrO2 radicals, probably by RMA(.) and RMAOO(.) radicals. The increase of period lengths in RMA-BZ systems with increasing sigma* values appears to be related to the bromination/enolization of the organic substrate as the determined enolization rates of RMA show.