Yes, the Oxford (serial) comma is optional.
We learnt that if the dependent clause comes at the end of the sentence then no comma is used:
He produced violin concertos, serenades, and divertimentos during this wonderful period.
But, if the dependent clause comes before the independent clause then a comma is required. Thus:
During this wonderful period, he produced violin concertos, serenades, and divertimentos .
So, I presume, in a sentence with two independent clauses the puncuation would be:
His tenure lasted till 1777, and he produced violin concertos, serenades, and divertimentos during this wonderful period.
But, if we move "during this wonderful period" within the sentence, will the punctuation be:
His tenure lasted till 1777, and during this wonderful period, he produced violin concertos, serenades, and divertimentos.
OR:
His tenure lasted till 1777, and, during this wonderful period, he produced violin concertos, serenades, and divertimentos.
Thanks,
S