In [4], Brown proved that the I-function of a toric fibration lies on the overruled Lagrangian cone of its
$g=0$
Gromov–Witten theory, introduced by Coates and Givental [8]. In this paper, we prove the theorem for partial flag-variety fibrations. To do so, we construct new moduli spaces generalising the idea of Ciocan-Fontanine, Kim and Maulik [7].