We present a phase-space analysis of two stellar groups at the core of the Orion complex: Briceño-1 and Orion Belt Population-near (OBP-near). These stellar substructures are identified with the clustering algorithm, Shared Nearest Neighbor (SNN), using Gaia eDR3 astrometry. Space motions for the groups’ stars are derived with eDR3 proper motions and radial velocities from APOGEE-2, GALAH DR3, and Gaia DR2. A clear signature of radial expansion from a common center between the two groups is evident and is one of the most coherent examples of young cluster dissolution in a massive star-forming region. We extend our analysis to the thirteen other stellar groups identified by SNN and demonstrate that this coherent expansion is confined to Briceño-1 and OBP-near whereas the other groups show a more complex dynamical history. The exact physical mechanism invoking this expansion remains unclear, however, an extant 3D dust map reveals that the two groups lie at the center of a dust shell suggesting that their motions may be tied to strong stellar feedback influencing the ISM.