Counting is still under way following an election on Thursday that capped a near-decade long transition to democracy from monarchy and a civil war in which more than 17,000 people died.
Oli, 65, has vowed to form a government that lasts its full five-year term, something no prime minister has achieved since parliamentary democracy was established in 1990.
His campaign has called for the extension of the Chinese railway network into Nepal and implement of hydroelectric, airport and other infrastructure projects to create jobs.
"We can expect Oli to lead a stable government with the Maoists as strong allies," said Bipin Adhikari, a constitutional expert. "Once there is political stability he can implement a development agenda and attract foreign investment."
Instability has spooked investors, curbed growth, spurred corruption and slowed reconstruction after a 2015 earthquake that killed 9,000 people.
"If Oli leads the new government, he will be forced to be pragmatic in maintaining a geo-political balance with both," said Kunda Dixit, editor of the weekly Nepali Times.
Final election results are expected to take about a week, election officials said.
Home to Mount Everest, Nepal is one of the world's poorest countries.
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