Long before PBS there was NBC Television Opera, which not only presented standard repertoire, but new or unfamiliar works like Poulenc's Dialogues of the Carmelites, Prokofiev's War and Peace, Britten's Billy Budd, and Menotti's The Labyrinth. This series was responsible for the 1951 broadcast, and subsequent performances, of Amahl and the Night Visitors, which I first saw while recuperating from pneumonia around 1955.
Omnibus - was that on CBS? - presented abridged versions of the Met's Die Fledermaus and La Perichole, along with plays - The Apollo of Bellac by Giraudoux, She Stoops to Conquer, Sophocles' , etc. - excerpts from musicals, ballets, Leonard Bernstein conducting Handel's Messiah, etc.
The ones I really looked forward to were Hallmark Hall of Fame broadcasts: Eva le Gallienne's Alice in Wonderland, Julie Harris in Victoria Regina, Roddy McDowell and Lee Remick in The Tempest, Mary Martin in Born Yesterday, Christopher Plummer in Cyrano de Bergerac, the Lunts in Magnificent Yankee, and too many others.