He had a large studio and was one of the most influential painters working in Siena and the surrounding towns in the second half of the fourteenth century.
From 1356 he worked in the Collegiata, the principal church of San Gimignano, some 30 km from Siena, where he painted the entire side of the left aisle with a cycle of frescoes of Scenes from the Old Testament; the completed work was signed and dated in 1367.
In the early part of 1367 he was employed, along with Giacomo di Mino, in the decoration of the Cathedral of Siena.
In 1389, Bartolo, assisted by Luca Thome, painted the altarpiece for the Shoemakers' Company, in the Cathedral of Siena, and continued from that year until his death to furnish altarpieces for the cathedral and other churches of Siena, all of which have now disappeared.
His style is marked by the rejection of the concrete figures associated with Pietro Lorenzetti to instead favor flatter decorative otherworldly compositions in the manner of Simone Martini and Duccio.