Harbour founded the Ocular Oncology Service at the Washington University School of Medicine in St. Louis, where he was the Paul A. Cibis Distinguished Professor of Ophthalmology & Visual Sciences.

In 2012, he was recruited to the Bascom Palmer Eye Institute and Sylvester Comprehensive Cancer Center at the University of Miami as professor of ophthalmology, biochemistry, and molecular biology.

Harbour developed a keen interest in research during his undergraduate years at Texas A&M, where he studied the function of the copper protein ceruloplasmin in the laboratory of Dr. Edward Harris.

This discovery added to increasing recognition of the retinoblastoma tumor suppressor pathway as a common target of mutation in the vast majority of human cancers.

[4] When Harbour joined Washington University in 1996, he undertook a three-year postdoctoral research training program in molecular oncology, which resulted in a first author publication in the journal Cell showing that the retinoblastoma protein is regulated by successive phosphorylation events.

[8] In 2012, the Harbour lab discovered that the histone deacetylase inhibitors may be repurposed to also treat uveal melanoma by reversing the high risk class 2 profile.

Subsequently, this discovery has formed the basis for an innovative clinical trial at Bascom Palmer Eye Institute and Sylvester Comprehensive Cancer Center to assess the use of the histone deacetylase inhibitor Vorinostat in patients with high risk uveal melanoma.

[12] In 2020, the Harbour lab was the first to publish single-cell sequencing data in uveal melanoma, showing previously unrecognized evolutionary and microenvironmental complexity in primary and metastatic tumors.

In 2008, he received the Rosenthal Award from the Macula Society for an "individual under 50 years of age whose work gives high promise of a notable advance in the clinical treatment of disorders of the eye."