The crystallization of oxyethylene/oxybutylene (E/B) diblock copolymers has been studied by simultaneous SAXS and WAXS. The copolymers crystallized from their melts (disordered, lamellar, or hexagonal) with folded E blocks. Rapid crystallization (quench) of lamellar melts was accompanied by a change in length scale and led to structures with multiply-folded E blocks and the B blocks slightly stretched from their melt conformation. Quenching the hexagonal melts gave no change in length scale and led to structures with multiply-folded E blocks and the B blocks unstretched from their melt conformation. These metastable folded structures formed during rapid crystallization did not unfold on heating but could be self-seeded to grow equilibrium once-folded (or multi-folded) structures. The folded states are discussed in terms of contributions to the Gibbs energy of crystallization from E-block folding and B-block stretching.