He came to Genoa to study law but devoted his time and energy to painting. He studied with Domenico Fiasella from c. 1664?9, and in this period he may have painted scenes in the style of Giovanni Andrea de?Ferrari, Fiasella and Giovanni Battista Casone. He assisted Fiasella on the altarpiece St Clare Repulsing the Saracens (1667; Montoggio, parish church). Probably after the death of Fiasella in 1669, Gregorio went to Parma, perhaps accompanied by Giovanni Battista Merano and Andrea Sighizzi (d 1684), from whom he may have acquired his skill in quadratura design. In Parma he abandoned the monumentality of Fiasella抯 art, and began to develop a softer, more lyrical manner. Two paintings, the Rest on the Flight into Egypt and the Virgin with St Jerome and the Magdalene (both untraced, are mentioned by Ratti as. During his years in Parma, Gregorio may have exchanged ideas with Giovanni Battista Gaulli, Merano

The paintings executed after his return (c. 1671) to Genoa suggest the influence of these artists and are distinguished by the graceful elongations and vertical spiral movement of the figures, which resei and Bernardo Schiaffino. They became more undulating and more tightly modelled by the end of the century. Two canvases inspired by Correggio, St Francis Comforted by an Angel and Rest on the Flight into Egypt (both Genoa, S Siro), are dated to c. 1674?5. Domenico Piola is said to have admired Gregorio抯 work so much that in 1674 he gave his daughter to Gregorio for a wife. The marriage encouraged a harmonious working relationship, which contributed to the prestige of the Casa Piola workshop, founded in the 1660s. In S Siro, Genoa, Piola painted a vault, the Glory of St Gaetano (1674), and in 1676 he received payment for the adjoining vault, the Glory of St Andrew Avellino, frescoed by Gregorio in 1676?7.