From Grove: Born in New York, studied in Leipzig and Paris (Carl Reinecke wrote a Albumblatt für Herrn Oscar Weil zu freundlichem Erinnern in 1861); served in the Civil War, moved to San Francisco in 1868 and composed (among other works?) piano works, songs, several operas and operettas (see Grove and also the Oscar Weil Papers above which lists works not mentioned there).
His "Spring Song" (no.2 of his Opus 10 set) was several times recorded in the early 1910s (see UCSB Victor Discography.)