At the age of six, Oliver and his brother Leslie,[3] three years his elder, were hired by Walter M. Morosco (1846–1901) to perform in his acrobatic troupe, the Royal Russian Circus, then a regular attraction at Woodward's Gardens, a popular San Francisco amusement park.
He took over the lease on the troubled Burbank Theatre and soon made it a success with a series of stock companies and shows featuring the popular actors of the day.
He also entered into a partnership with the Belasco-Meyer interests of San Francisco to take over management of their theaters on the west coast, including the Belasco Theatre in Los Angeles, the Burbank's chief rival as a stock house.
Though Los Angeles remained his home, Morosco began producing plays in New York City in 1906 and mounted over 40 productions on Broadway including Peg o' My Heart and The Bird of Paradise both starring Laurette Taylor.
He contributed lyrics to a Victor Schertzinger song he had added to L. Frank Baum and Louis F. Gottschalk's musical, The Tik-Tok Man of Oz, which he produced in 1913.