The influence of zeolite heteroatom composition on the electron density and catalytic activity of a supported Ni cation is examined. Ni–[X]-Beta catalysts, where X = Al, Ga, Fe, or dealuminated, were synthesized and characterized with probe molecule adsorption with FTIR spectroscopy and C₂H₄ dimerization catalysis. It was observed via CO adsorption that supported Ni cations were increasing in electron density in the order: [Fe] > [Ga] > [Al]. C₂H₄ dimerization activity increased with increasing electron density of the Ni cation. Despite similarities in reported acid site strength, the acid sites on [Fe]-Beta in this work had significantly lower activity than those on [Ga]-Beta for the skeletal isomerization of linear butenes as well as C₂H₄ dimerization. Introducing H₂ as a reactant resulted in a decrease in dimerization activity for Ni–[Al]-Beta and Ni–[Ga]-Beta but an increase for Ni–[Fe]-Beta. The selectivity and activity of Ni–[DeAl]-Beta changed dramatically with the introduction of H₂, which subsequently converted all C₂H₄ with ca. 100% selectivity towards C₂H₆ (even with a lower space velocity relative to without H₂). These results demonstrate the ability of heteroatom composition to tune catalysis by using C₂H₄ dimerization catalysis as a test reaction with zeolite Beta supported Ni catalysts.