Understanding and controlling the evolution of the graphene oxide (GO) structure during thermal reduction is critical for tailoring the reduced GO (rGO) properties for applications in energy storage and generation, electronics, and membrane. While previous in-situ diffraction studies have largely focused on interlayer collapse along the (00ℓ) direction, the fate of the in-plane lattice and stacking registry has remained elusive. Here, we use synchrotron powder X-ray diffraction, complemented by in-/out-of-plane laboratory measurements on films, to monitor the (100)/(101) region of GO during reduction. Applying the Basic Structural Components (BSC) model, we quantitatively track turbostratic single layers, AB-paired bilayers, and short Bernal ABA sequences, alongside the evolving in-plane lattice parameter. We uncover a transient, rate-selected amorphous-like regime (140–190 °C) where the (100) intensity nearly vanishes, followed by divergent kinetic pathways: fast ramps trap AB-enriched but ABA-deficient states even at 900 °C, whereas slow ramps (≤0.5 °C min -1 ) below ∼240 °C enable progressive AB ordering and the emergence of short-range ABA. These results establish a process–structure map linking thermal history to stacking registry and in-plane strain. Beyond elucidating the reduction mechanism, our work outlines kinetic guidelines to deliberately trap amorphous-like 2D carbon or promote AB/ABA order, providing a controllable pathway to engineer interlayer coupling in rGO. • Kinetics determine A/AB/ABA stacking and in-plane strain in GO thermal reduction • Fast ramps create an amorphous in-plane state; dwell restores turbostratic order with AB • The in-plane peak recovers logarithmically; growth is limited by defect pinning • Slow ramps up to 240 °C promote AB and short-range ABA stackings • Thermal reduction yields an in-plane (d 100 ) contraction that persists up to 900 °C