Book 28 of On Nature ends with:
Quote from Epicurus, On Nature, Book 28And now I think I have finished prattling to you this twenty-eighth installment of our consecutive lecture series.
He uses the word ἀκρόασις "hearing, hearkening or listening to" where "lecture series" is the translation even though its a written work. The work is also written partially as a dialogue between Metrodorus and Epicurus, using first and second pronouns. This strikes me as different than Plato's dialogues in that he created characters (including his dead teacher, Socrates). I would see On Nature being more like transcripts of actual teachings.
We know that at least Herodotus, Pythocles, and Menoikeus were literate: We literally have Epicurus' letters addressed to them. We know the Founders were all literate and wrote extensive treatises. We know Philodemus was prolific in his writings. We know that Diogenes, living in Oenoanda, was literate and also thought enough people could read that his inscription would be useful to passers-by. But if the popularity of Epicurus' philosophy was as wide spread as to make Cicero clutch his pearls, I doubt literacy was widespread throughout the community.
Bart Ehrman has a relevant blog post talking about early Christian communities that includes:
Quote from EhrmanBlogSo let’s assume that [the literacy rate in Graeco-Roman times] was 20%. That would mean that an average church, with 70 members, of whom 20 were adult males, would have, on average four who would read. And of course their reading abilities would cover a wide range: some could probably read very painstakingly and slowly, maybe one or two could read pretty well – it’s hard to say. Overall, there would be, around the year 100, 400 Christians (in the entire world) who could read.
He goes on to say that those who could read then would be leaders in their communities. I would think this would hold for Epicurean communities.
I found an interesting lecture online about reading, even silently, in the ancient world: https://www.gresham.ac.uk/watch-now/anci…torical-context
There's also the encouragement - even requirement - for ancient Epicureans to commit epitomes to memory. That's why Epicurus provided summaries of his work, so that the written document became superfluous. For students who were not fully literate, this would have meant working with a teacher to internalize the most important works.
Epicurus to Pythocles (emphasis added): To aid your memory you ask me for a clear and concise statement respecting celestial phenomena ; for what we have written on this subject elsewhere is, you tell me, hard to remember, although you have my books constantly with you. I was glad to receive your request and am full of pleasant expectations. [85] We will then complete our writing and grant all you ask.
Epicurus to Herodotus: For those who are unable to study carefully all my physical writings or to go into the longer treatises at all, I have myself prepared an epitome56 of the whole system, Herodotus, to preserve in the memory enough of the principal doctrines,57 to the end that on every occasion they may be able to aid themselves on the most important points, so far as they take up the study of Physics. Those who have made some advance in the survey of the entire system ought to fix in their minds under the principal headings an elementary outline of the whole treatment of the subject. For a comprehensive view is often required, the details but seldom.
Epicurus encourages Menoikeus to study what he's written night and day with a like-minded friends (so they can read the work to each other?), likely to impress it into his mind so he has the information asleep and awake.
I realize Philodemus railed against Epicureans who had strayed from studying the books, but if On Nature really was a series of lectures, this could just as easily meant getting back to attending lectures from my perspective.