This study has provided information about the performance of magnesium hydroxide in two EVA copolymers while also comparing the performance of the copolymers. The low-ethylene EVA tolerates the higher filler loadings of magnesium hydroxide more readily than the high-ethylene EVA. On the other hand, the latter has certain advantages, exhibiting higher tensile and tear strength values. Increasing the loading of magnesium hydroxide has a beneficial influence on tear strength and water adsorption. It was also interesting to note the differences in limiting oxygen index between the two sets of filled compounds. Compared with EPDM, much lower filler loadings are needed to achieve similar values of oxygen index. Taking all properties into account, the range 100 to 150 phr of magnesium hydroxide would be recommended for further development work.