Ti1-xAlxN coatings deposited on cutting tools by cathodic arc evaporation (CAE) are widely used in industry for machining applications. The demand for higher cutting speeds and feed rates, combined with a reduction of coolants and lubricants, leads to increasing tool temperatures, resulting in reduced tool lifetime or premature failure due to oxidation. Different quarternary coatings based on Ti1-xAlxN were found to have improved wear and oxidation behavior compared to the ternary system. The aim of this work was to determine the influence of alloying small amounts of Si and B into Ti33Al67N coatings, grown by CAE, at the expense of the Ti content. Furthermore, the bias voltage was varied during deposition, to examine a possible influence on the oxidation resistance. Various annealing conditions were chosen to oxidize the as-deposited coatings, to investigate the progress of oxidation, with respect to oxidation- time and temperature. The coatings were characterized by X-ray diffraction and Raman spectroscopy. Scanning electron microscopy was used to measure the oxide layer thickness from cross-sectional fracture surfaces for a quantitative evaluation of the oxidation resistance. Transmission electron microscopy was used to gain information on oxide layer structure and composition. It was found that both Si and B have a significant positive influence on the oxidation behavior of Ti1-xAlxN, while an increase of the bias voltage leads to a deteriorated oxidation resistance.