Ephrem Mtsire puts him at the peak of his career in the sixth year of Basil II (982).

His most important work by far, however, is the menologion, which Albert Ehrhard labelled "a revolution in the field of hagiography".

He did not merely collect and arrange pre-existing saint's lives, but also reworked them, standardizing their language and embellishing their rhetorical style to bring them in line with the Atticism of the day.

[5] For his menologion, Symeon received praise from Nikephoros Ouranos and Michael Psellos addressed to him an encomium.

In particular, Delehaye found that Symeon or his immediate sources sparsely added materials of their own drawn from other places.

[9] Michael Psellos compiled Symeon's biography (c. 1050) and he composed a liturgical office for him.