While the Republicans have 51 votes in the 100-member chamber, 60 votes are required to break a filibuster.
Oli received 338 votes from the 597-member chamber, defeating his predecessor Sushil Koirala, who received 249 votes.
Three senators of the 35-member chamber voted against the bill, and a fourth abstained; all are Democrats.
But Mr. Schwarzenegger had threatened to seat him anyway because a majority of the 80-member chamber had not voted against him.
He joined nine other constitutionally mandated "designated" senators, including several of his closest former military aides — men like General Canessa — in the forty-eight-member chamber.
The INLD contested the 2000 assembly elections in alliance with the BJP and won 47 seats in the 90-member chamber; the BJP added another six seats.
Two socialist backbenchers said they would henceforth sit as independents, reducing the party's parliamentary majority to a bare minimum of 151 seats in the 300-member chamber.
Mr Gul, a pious Muslim whose earlier bid for the job sparked political turmoil, won 341 votes in the 550-member chamber.
"The People's Party and the Freedom Party have a majority of seats in Parliament," he said, referring to the two parties' 104 seats in the 183-member chamber.
The Senate has been deadlocked since June 8, when Senator Pedro Espada Jr., a Democrat, defected to the Senate's 30 Republicans, leaving the 62-member chamber evenly divided.
Supporters of the resolution, speaking before the vote, said they were confident of achieving the necessary nine votes in the 15-member chamber.
