Nowadays, many researchers are intensively trying to develop novel environmentally friendly composite materials for construction with a view to replace widely used Portland cement (PC). Current hopes are pinned on the use of materials based on reactive magnesia. In this case study, composites prepared from magnesium oxychloride cement (MOC), ground waste glass, and either quartz sand or foam glass were prepared and analyzed in detail. The main aim was to design and develop novel composites with low unit weight, good thermal insulation performance, and high water damage resistance. In addition, the application of secondary-raw materials as a partial substitution for common fillers was accented. The properties of fresh and matured composites were studied and analyzed within the framework of a complex experimental campaign involving phase composition assessment, structural, textural, mechanical, hygric, thermal, and durability parameters testing, as well as the identification of main chemical bonds in the formed hardened materials. The usage of ground waste glass led to a significant drop in porosity, densified microstructure, enhanced compressive strength, reduced water ingress, and improved durability. In general, the prepared composites provide properties and performance, which make them promising eco-efficient alternatives to PC-based construction composites.