A previous study of the system (Li,Na,K)TaO3 was extended to include the metaniobates. Glasses were made by twin‐roller‐quenching 33 compositions in the three pseudobinary systems as well as in the pseudoternary system composed of LiNbO3, NaNbO3, and KNbO3 and in the pseudobinary M(Nb,Ta)O3 where M is Li, Na, or K. Glasses were obtained in all but the most Na‐rich regions. Study of these metastable compositions by X‐ray diffraction and differential thermal analysis showed the appearance of four metastable crystalline phases on crystallization, one centered at KNbO3, one with an extended occurrence in the ternary system (Li,Na,K)NbO3, one centered about Li0.6Na0.4NbO3, and one at KNb0.25Ta0.75O3. There is some evidence for a subsolidus two‐glass region in the system (K,Na)NbO3. The ionic conductivity of the LiNbO3 glass was ∼10−5Ω−1 cm−1 and the dielectric constant shows ferroelectricity‐like behavior. Some infrared absorption data gave almost identical curves for the glass and the metastable crystalline phase, which was the first to crystallize.