Thin films, consisting of Transition Metal Carbides (TMCs), are known for their remarkable thermal stability, with melting points reaching up to 4000 °C, and their excellent mechanical properties, including exceptional hardness. These properties make Physical Vapor Deposited (PVD) TMCs indispensable materials for challenging applications in the aerospace and tooling industries. Nevertheless, their limited oxidation resistance inspires the alloying of strong oxide formers such as Al and Si to improve their high-temperature performance. Setting the focus on metastable, fcc-structured, TM-X-C (TM = Ti, Zr, Hf, Ta, W and X = Al, Si) solid solutions, Density Functional Theory (DFT) was used in order to access the metastable solubility trends, by the means energy of formation and unit cell distortion. In a second step, these theoretical findings are correlated with an experimental approach in which over 260 different compositions within these ten material systems are grown by combinatorial magnetron sputtering. Phase formation, mechanical properties, and oxidation resistance are subsequently analyzed by X-ray diffraction, nanoindentation (CSM method), and Transmission Electron Microscopy (TEM) for selected states. The comprehensive analysis of structure-property relationships of these ternary TMC thin films provides crucial insights into the so-far relatively unexplored phase space and opens up opportunities for advanced applications. Keywords: Carbides; Phase screening; Structure-mechanical properties; Oxide formers; PVD;