How old is an oak tree before it produces its first acorns?

AnswerThis depends on tree's specific condition, species, habitat, stress level ect, and I've heard anywhere from 10-30 years depending on the species.

The best acorns for human/ animal consumption are that of Swamp White Oak (Quercus bicolor). They have the lowest tannin levels (bitter taste) of all of the north-east hardy white oaks and are healthy, sustainable, and pretty good once leached. It can also be used to create flour for bread.

There was a study through University of Missouri called GRAFTING INFLUENCES ON EARLY ACORN PRODUCTION IN SWAMP WHITE OAK that showed you can achieve prolific and early bearing as early as 4 years by grafting a prolific nut producing Swamp White Oak scion onto a regular White Oak (Quercus Alba) rootstock.