In a previous short communication (Macromolecules 2002, 35, 8251-8254), we reported a unique morphology in binary miscible crystalline poly(ethylene succinate) (PES)/poly(ethylene oxide) (PEO) polymer blends, in which two kinds of spherulites, corresponding to each component, respectively, grew simultaneously and PEO spherulites continued to crystallize inside PES spherulites on contact, forming interpenetrated spherulites. In the present work the effects of blend composition and crystallization temperature on the crystalline morphologies of PES/PEO blends were studied by optical microscopy in detail. The unique morphology of PES spherulites penetrated by PEO spherulites was observed for the blends with PEO content ranging from 50 to 90% in a wide crystallization temperature range. Furthermore, three novel and interesting crystalline morphologies were found depending on blend composition and crystallization temperature. First, new boundaries were formed by the growth of a single PEO spherulite itself after penetrating into PES spherulites because of the change in the growth direction. Second, both components penetrated each other and formed interpenetrated spherulites. Third, PES and PEO formed a special kind of blended spherulite that nucleated from the same site and showed two growth fronts with PEO growing faster than PES. The growth rates of both components were studied; furthermore, much more attention has been directed to the study of the observed growth rates of both types of spherulites when they developed freely in the undercooled melt and when they were forced to penetrate each other. The blend composition and crystallization temperature effects on the various crystalline morphologies were summarized in PES/PEO polymer blends, which should be of great interest and importance for a better understanding of the crystallization and morphology in miscible crystalline/crystalline polymer blends.