He visited Rome, became an ardent student of the antique, and like Bernardino — distantly related to him — he combined a Lombard and Roman traditions.

[citation needed] According to the 1913 Catholic Encyclopedia, "His numerous paintings are grandly and reverently conceived, freely drawn, vigorously coloured, lofty in style, and broadly handled.

When he was twenty-seven, Giulio executed a Virgin and Child with Sts Celsus and Nazarus for the church of Sant'Abondio.

This painting is regarded as his masterpiece; the Catholic Encyclopedia praises it as "masterly in the freedom of its drawing and in the splendour of its color."

An altar-piece in San Sigismondo and his Labours of Hercules were engraved by Giorgio Ghisi.