Coating materials for sliding wear protection at high temperature should include an oxidation-resistant metal matrix, which confers ductility and thermal expansion matching to stainless steel or superalloy substrates, and a refractory hard phase to provide hot hardness. Based on these criteria, oxide dispersion strengthened (ODS) CoNiCrAlY powders containing 2, 10 and 30 wt.% of fine Al2O3 particles were manufactured by high-energy ball milling. These powders were processed into approx. 300 micron-thick coatings by vacuum plasma spraying (VPS). The unreinforced CoNiCrAlY powder was also sprayed as a reference. Ball-on-disc sliding tests performed in air at 750 °C against an Al2O3 counterpart show that, in comparison to the uncoated substrate, the wear rates of the coatings decrease with increasing Al2O3 content, except for the sample containing 10 wt.% Al2O3. The wear mechanisms of all coatings include adhesion and tribo-oxidation. Specifically, the coatings tend to develop thick (>1 micron) oxidized tribo-layers, also termed glazes, which play a key role in restrain adhesive wear of the metal phase. The composite coating with 30 wt.% Al2O3, in particular, develops a particularly stable and uniform glaze, which minimizes the wear rate. The mechanisms by which Al2O3 particles affect glaze stability are investigated and discussed.