With the increasing use of coated functionally graded materials (FGMs) in various industrial engineering, their accurate modeling is very theoretically challenging and therefore has attracted the attention of many scholars, especially for multilayer coated FGM nanostructures. To address this challenge, a new nanoplate model is proposed herein to characterize the buckling behavior of bilayer FG porous plates, which is capable of both geometrically thickness-stretching and physically microstructure-dependent effects. The materials are graded continuously through 2-directional by using a power law function. Two types of coated FG plates are investigated, Hardcore and Softcore FG plates. Based on the generalized field of displacement, a Quasi-3D higher-order shear deformation plate theory is proposed in this work by reducing the number of variables from six to five variables. The equilibrium equations are performed based on the virtual work principle and solved using the Galerkin method to cover various boundary conditions. The accuracy of the proposed solution was validated and it is in good agreement with the counterparts available in the open literature. The effects of microstructure-dependent length parameters, geometric parameters, and material property changes on the critical buckling load are studied in detail.