The structural design of pultruded glass fiber reinforced polymer (GFRP) beams and columns has been extensively studied, and various design methods have been proposed in the literature and adopted in standards. Most approaches address the coupled buckling interaction phenomenon but use separate formulations to handle failure modes governed by material crushing. However, in reality, failure involves a complex interaction between buckling and crushing. To address this limitation, this work proposes a universal methodology for designing pultruded GFRP members subjected to pure compression or major axis bending, accounting for the interactions among crushing, global buckling, and local buckling. The proposed ‘all-in-one’ methodology is based on the Ayrton-Perry approach and follows a two-step procedure: (i) calculation of local strength considering local buckling-crushing interactions, and (ii) computation of overall strength considering interactions between local strength and global buckling. Each step incorporates imperfection factors to indirectly account for pultrusion-induced geometrical and material imperfections, calibrated using experimental results reported in the literature. The database includes test data from I/H-sections, covering a wide range of local and global non-dimensional slenderness combinations. The results are compared with methods proposed in existing international standards (ASCE 74-23 and CEN/TS 19101:2022) and demonstrate that the proposed method provides superior predictions.