@fmacanadaguy @JeremyECrawford I've run it as yes
— Mike Mearls (@mikemearls) April 28, 2016
@G0DL1K3D3V1LSorry if this is a late question, but if said character also has Warcaster, can he cast a Warcaster legal spell? War Caster does, indeed, work with opportunity attacks, as specified in its third benefit.
— Jeremy Crawford (@JeremyECrawford) March 6, 2017