Gap opening in a wide-enough doping range, whilst keeping high conductance outside this gapped state, has remained a grand challenge in graphene since decades. Here, we show a unique heterostructure of Bernal-stacked bilayer graphene (BLG) atop few-layered CrOCl, which enables a surface state in CrOCl under vertical electric fields, and it promotes electron-electron(e-e) interactions in BLG via Coulomb long ranged coupling. Consequently, at the charge neutral, a crossover from single particle insulating behavior to an unconventional correlated insulator is seen, below a critical temperature. The over1 GΩ insulating ground state exists in a widely accessible gate range, and can be switched into a metallic state with an on/off ratio up to 107, by applying an in-plane electric field, heating, or by gating. A logic inverter using such correlated insulator is demonstrated, despite that it works still at low temperature. Our findings of the correlated insulating phase in CrOCl/BLG heterosystem paves the way for future engineering of exotic quantum electronic states in the paradigm of interfacial charge coupling.