On his arrival at Berkeley, Birge sought collaboration with the Berkeley College of Chemistry, then under the leadership of Gilbert N. Lewis. However, Birge's championing of the Bohr atom led him into conflict with the chemists who defended Lewis' earlier theory of the cubical atom. Birge was unafraid of scientific controversy and persevered with his course on atomic structure, attracting future Nobel Laureates in chemistry William Francis Giauque and Harold Clayton Urey. His work ultimately led to the development of the discipline of physical chemistry. His work on molecular spectra included the devleopment of the Birge-Sponer method.
Birge's later work arose from his initial bewilderment at the variety and inconsistency among measurements of the fundamental physical constants. His interest led to a broad mastery of all branches of the physical sciences and gave fruit with many publications, in particular, a 1929 paper in Reviews of Modern Physics that recommended a standard set of values for the constants based on earlier published results. There ensued a frustration with the conventional methods of statistics as applied in physical science which led to a collaboration with W. Edwards Deming. Following their 1934 joint paper in Reviews of Modern Physics, their approaches diverged with Deming following the work of Walter A. Shewhart while Birge became interested in the more conventional statistical approaches of least squares and maximum likelihood. Birge's interest in statistics led him to the investigation of parapsychology in which he conducted many experiments without finding any conclusive results.
Birge was an active administrator and was the architect of the Berkeley department's prestige, attracting physicists such as Robert Oppenheimer and Ernest Lawrence. However, during the McCarthy era in 1949, the Regents of the University of California enforced an anti-communist oath to be signed by all employees. Though an outspoken critic of the oath, after much searching of conscience, Birge decided that his loyalty to the department and the university demanded that he sign and fight from within for freedom of speech. Many of his colleagues did not sign and were dismissed.
Birge died in Berkeley, California. His honours include: