  Let $\mathcal{S}$ be a finite thick generalized quadrangle, and suppose that
$G$ is an automorphism group of $\mathcal{S}$. If $G$ acts primitively on both
the points and lines of $\mathcal{S}$, then it is known that $G$ must be almost
simple. In this paper, we show that if the socle of $G$ is $\mathrm{PSL}(2,q)$
with $q\geq4$, then $q=9$ and $\mathcal{S}$ is the unique generalized
quadrangle of order $2$.
