The aim of the present paper is to examine the effect of a quasi-periodic gravitational modulation on the onset of convective instability in Hele-Shaw cell. The quasi-periodic modulation considered here consists in a modulation having two incommensurate frequencies. This study is an extension of a previous work by Aniss et al. [10] in which only a periodic gravitational modulation was considered. We have shown that for P r = O(1) or P r >> 1, the gravitational modulation has no effect on the convective threshold as expected. However, for P r = O(ǫ 2 ), it turns out that a modulation with two incommensurate frequencies has a stabilizing or a destabilizing effect strongly depending on the frequencies ratio.