The liquidus temperatures, TL, of rare earth-alumino-borosilicate glasses were measured as a function of glass composition. The TL values ranged from 1153°C to 1405°C. Three primary crystalline phases were identified in the study. The most frequently encountered was a rare earth silicate phase in which the TL values ranged from 1153°C to 1405°C. A12O3 was encountered in glasses with an A12O3:SiO2 mass ratio greater than 1, with TL values ranging from 1242°C to 1305°C. Alumino-silicate crystals were encountered as the primary phase in glasses with less than 43 mass% of mixed rare earth oxides (Ln2O3) with TL values between 1164°C and 1255°C. A linear relationship between total mixed rare earth oxide concentration and TL was found within all three primary phase fields. In the rare earth silicate primary phase field, normalizing the Ln2O3 concentration with its mean ionic radius enhanced this linear relationship.