  We give a Casselman-Shalika type formula for unramified Speh representations.
Our formula computes values of the normalized spherical element of the $(k,c)$
$\psi$-Whittaker model of a Speh representation at elements of the form
$\operatorname{diag}\left(t, I_{(k-1)c}\right)$, where $t$ is a diagonal
element. The formula expresses these values in terms of modified
Hall-Littlewood polynomials evaluated at the Satake parameter attached to the
representation. Our proof is combinatorial and very simple. It utilizes
Macdonald's formula and the unramified computation of the Ginzburg-Kaplan
integral. This addresses a question of Lapid-Mao.
