He has been a visiting scientist at CERN (ISR, LEP Collider), Brookhaven National Laboratory, Fermilab, Rutherford Appleton Laboratory, University College London and Imperial College London.
As spokesman for D0 from 1983 to 1993, and co-spokesman with Hugh Montgomery from 1993 to 1996, Grannis led the D0 experiment from its inception through the end of Tevatron Run I. D0 extended our understanding of particle physics through its co-discovery with CDF of the top quark in 1995; precise measurements of the W boson mass and couplings; extensive studies of QCD using jets, gauge bosons and b-quarks; and searches for a variety of signatures of new physics.
[2] From 2014 he has again served as co-spokesperson of D0, with Dmitri Denisov.From 2001 to 2005, Grannis was the chair of the Department of Physics and Astronomy at Stony Brook University.
Grannis has worked to bring an electron positron collider capable of studying the Higgs boson and related questions regarding electroweak symmetry breaking since 1998.
Grannis' autobiography, ``An Experimental Life", appeared in Annual Reviews of Nuclear and Particle Physics, 74, 1 (2024).