Abstract: The study of microbial complexes in organo-accumulative horizons of Antarctic soils (Cryosols, Leptosols) at the Larsemann Hills and Schirmacher oases and on King George Island has been carried out by the fouling glass method. This method allows one to study the taxonomic composition of microorganisms, features of their morphology, inter-organism interactions, and spatial organization of the complex of microorganisms, as well as to simulate the processes of colonization of mineral surfaces. The investigated microbial complexes can be subdivided into four groups with respect to dominant microorganisms: (1) diverse microbial complexes of King George Island with a considerable portion of diatoms among algae and with a predominance of mycelium in the fungal biomass; (2) complexes of lichen–moss, moss, and algal–moss associations in lake basins with a greater proportion of eukaryotic and coccoid cyanobacteria and with mycelium and sporous forms of micromycetes; (3) complexes of moss and algal–moss associations in the bottoms of wet valleys with a higher proportion of filamentous cyanobacteria and with the absence of fungi, or their presence in the form of short chains of chlamydospores; and (4) hypolithic microbial complexes of rock baths in dry rocky habitats, where the fouling of glasses did not take place. The microbial complexes in different glass samples taken in February–March in different years proved to be at different stages of development. Microscopic mycelium of fungi was not abundant in all algae and moss associations; in some, it was practically absent. Among algae, not cyanobacteria, but eukaryotic algae dominated in a number of habitats: diatoms, green algae, and streptophytes. The totality of the complex features indicated the extremity of the habitat: one morphotype of melanized fungal mycelium dominated in a particular sample; there was no diversity of spore forms, which indirectly indicates a low taxonomic diversity of fungi; multiple chlamydospore formation and microcycles of development were common. Among cyanobacteria, brown and reddish coloration was often found, and the formation of biofilms on glasses was limited to microcolonies, while algal biofilms abundantly covered the soil of the studied horizons. Apparently, extended biofilms were formed over time exceeding the exposure time of the glasses. Hypolithic communities did not colonize new habitats (glasses) for several years of exposure, unlike the bottoms of hydromorphic valleys and lake basins in oases (glasses overgrown in a year) and King George Island (glasses overgrown in 10 days).