if we're counting concerti grossi (which aren't the same as concertos for orchestra even in definition- they divide the orchestra into a ripieno and a concertino section, which is not how a "concerto for orchestra" is conceived generally, which is a work in which the orchestra is all soloists at various times, more or less; this would not apply to the ripieno section of a Concerto Grosso, which is basically a concerto with a large section of soloists, a predecessor of the modern concerto for soloist(s) and orchestra (itself also an instrumental outgrowth of the vocal Baroque aria, but that's a related but other tale), that would probably be someone about four centuries before. Therefore the first post of the thread is still important...