During oocyte maturation, polar body extrusion results from two asymmetric meiotic cell divisions that depend on the chromosome–spindle complex migrating from the oocyte centre to a subcortical location. Li and colleagues report that this migration occurs in two phases during meiosis I. The first phase was slow and dependent on formin 2 (FMN2). FMN2 colocalized with endoplasmic reticulum structures that surround the spindle and promoted local F-actin nucleation, which pushed the chromosome–spindle complex away from the centre. The second phase was rapid, driven by cytoplasmic streaming and initiated upon activation of a cortical actin-related protein 2/3 (ARP2/3) complex as chromosomes approached the cortex.