Compositions in the series Ni2-xCoxGeMO3N (0 <= x <= 2.), Co2Ge1-xGaxMo3N (0 < x <= 0.7.), Co2-xFexGeMo3N (0 <= x <= 2), and Co2-xFexGe0.5Ga0.5Mo3N (0 <= x <= 0.8) have been synthesized by the reductive nitridation of binary oxides and studied by appropriate combinations of magnetometry, transport measurements, neutron diffraction, and Mossbauer spectroscopy. All of these compositions adopt the cubic eta-carbide structure (a similar to 11.11 angstrom) and show a resisivity of similar to 10(-3) Omega cm. No long-range magnetic order was observed in Ni2-xCoxGeMo3N, although evidence of spin freezing was observed in Co2GeMo3N. The introduction of gallium into this composition leads to the onset of antiforromagnetic ordering at 90 K in Co2Ge0.3Ga0.7Mo3N. The magnetic structure consists of an antiferromagnetic arrargement of ferromagnetic Co-4 groups, with an ordered magnetic moment of 0.48(9)mu(B) per cobalt atom. The same magnetic structure is found in Co0.5Fe1.5GeMo3N and Co1.2Fe0.8Ge0.5Ga0.5Mo3N. The former orders above room temperature with an average moment of 1.08(3) mu(B) per transition-metal site, and the latter at 228 K with an average moment of 1.17(4) mu(B) per site. The magnetic behavior of these compounds is discussed in terms of the electron count within each series.