The Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray Observatory (CGRO) provides solar-flare observation capabilities that represent a significant improvement over previous experiments. In this paper, we discuss the OSSE solar observation modes, give an overview of the solar-flare observations to date, and discuss in some detail the observations obtained during the June 1991 CGRO solar Target of Opportunity. We show evidence for time structure of flare hard X-ray (>100 keV) emission as short as tens of msec. Several nuclear deexcitation lines along with emission >10 MeV were seen from the four GOES X10+ flares observed by OSSE. Neutrons were observed from two of the flares. Preliminary results from a search of the OSSE flare database for nuclear emission from weak flares are presented and compared to results from a similar search of the Solar Maximum Mission Gamma-Ray Spectrometer database.