In Jesus and the Eyewitnesses, Richard Bauckham argues that the Gospels are records of eyewitness testimony (oral history carefully collected from the individuals who were involved) rather than oral traditions (anonymous stories passed down collectively in the community):
If, as I shall argue in this book, the period between the “historical” Jesus and the Gospels was actually spanned, not by anonymous community transmission, but by the continuing presence and testimony of the eyewitnesses, who remained the authoritative sources of their traditions until their deaths, then the usual ways of thinking of oral tradition are not appropriate at all. Gospel traditions did not, for the most part, circulate anonymously but in the name of the eyewitnesses to whom they were due. Throughout the lifetime of the eyewitnesses, Christians remained interested in and aware of the ways the eyewitnesses themselves told their stories. So, in imagining how the traditions reached the Gospel writers, not oral tradition but eyewitness testimony should be our principal model….
[T]estimony — the stories told by involved participants in the events — was not alien to ancient historiography but essential to it.
Bauckham discusses this in the video below (or see here for an even shorter summary of the ideas he contends for in his book).