NBC International Limited Presents 1978

it DID debut in da fall of '79.

Technically, this peacock debuted much earlier (around the later years of the NBC Snake Logo, actually), but was replaced along with the Snake logo by the Proud N of the 1970's. The combo didn't happen until around fall of '79, so this wasn't '78

I saw that NBC 'Proud N' logo behind Justin Timberlake on the frame on the wall in the Saturday Night Live 'Five-Timers Club monologue skit.

1979

The peacock was first used in 1956 to highlight color programming. It didn't become part of NBC's main logo until 1979, and didn't become the network's sole logo until 1987.