Hesiod’s Works and Days (trans. H.G. Evelyn-White) on the Ages of Man:

First of all the deathless gods who dwell on Olympus made a golden race of mortal men who […] lived like gods without sorrow of heart, remote and free from toil and grief: miserable age rested not on them; but with legs and arms never failing they made merry with feasting beyond the reach of all evils. When they died, it was as though they were overcome with sleep, and they had all good things; for the fruitful earth unforced bare them fruit abundantly and without stint. They dwelt in ease and peace upon their lands with many good things, rich in flocks and loved by the blessed gods.

But after earth had covered this generation […the gods] made a second generation, which was of silver and less noble by far. […] A child was brought up at his good mother’s side a hundred years [… but in adulthood] they lived only a little time in sorrow, for they could not keep from sinning and from wronging one another.

[W]hen earth had covered this generation also […] Zeus the Father made a third generation of mortal men, a brazen race, sprung from ash-trees; and it was in no way equal to the silver age, but was terrible and strong. They loved the lamentable works of Ares and deeds of violence; […] terrible though they were, black Death seized them, and they left the bright light of the sun.

On good conduct:

Neither famine nor disaster ever haunt men who do true justice […] The earth bears them victual in plenty, and on the mountains the oak bears acorns upon the top and bees in the midst.

(Plato quotes this latter part in Republic 363.)

Acorns remind Don Quixote of a lost Golden Age (part I, chapter XI, trans. Rutherford):

Once the meat course was finished, a quantity of sweet acorns was spread on the sheepskins together with half a cheese […] After Don Quixote had satisfied his stomach he took up a handful of acorns and, gazing at them, held forth as follows:

“Happy the age and happy the centuries were those on which the ancients bestowed the name of golden, not because gold (so prized in our age of iron) was then to be obtained with ease, but because […] all things were held in common; no man, to gain his daily sustenance, had need to take any other pains than to reach up and pluck it from the sturdy oaks […] the running streams offered him their delectable and transparent waters […] and in the hollows of trees, diligent and prudent bees formed their commonwealths, offering to every hand, without requesting anything in return, the rich harvest of their sweet labours. […]”

This long harangue (which could well have been dispensed with) was pronounced by our knight because the acorns he’d been given had reminded him of the golden age; and so it occurred to him to offer these useless arguments to the goatherds, who listened without uttering a word, bemused and bewildered.

Plutarch, in his Life of Coriolanus 3.3 (trans. Perrin), also eulogizes the oak for its acorns and honey:

The oak, moreover, has the most beautiful fruit of all wild trees, and is the sturdiest of all trees under cultivation. Its acorn used to be food, and the honey found in it used to be drink for men […]

“Acorns in ancient texts” (Old European Culture, October 2015) lists more appearances of the ancient acorn. It seems to have been a meme that the aboriginal Arcadians were acorn-eaters, both in the most ancient times and soon after the death of Lycurgus (Didorus Siculus 9.36, Herodotus 1.66). Apollonius Rhodius’ Argonautica (trans. R.C. Seaton) describes those olden days:

As yet all the stars that wheel in the heaven were not; nor yet […] could aught be heard of the sacred race of the Danai. Apidanean Arcadians alone existed, Arcadians who lived even before the moon, it is said, eating acorns on the hills […] in the days when Egypt, mother of men of an older time, was called the fertile Morning-land […]

There is a modern thesis (1, 2) — maybe credible, certainly memetically successful — that the ancients were said to feed on honey dripping from the trees through a conflation of μέλι “honey” with μελίαι “ash-trees.” The manna ash exudes a sweet sap known as manna; recall that Yggdrasil, which drips with honey-dew, is an ash. (Hesiod, likewise, says the men of the Bronze Age descended from the μελίαι; but in that case the connection is with their warlike nature — ash is a good wood for spear-hafts.) In modern times, honeydew is the name for sap that’s already passed through an aphid or other sap-sucking insect (as opposed to oozing straight out of the tree perhaps through a hole made by an insect). This sweet secretion can indeed be collected by bees and turned into honey — Turkish pine honey is of this type.