The keenly contested elections could see the former political party of ousted ruler Suharto perform creditably, denting incumbent President Megawati Sukarnoputri's chances of winning a second term during the country's first direct presidential election on 5 July.
More than 147 million voters are eligible to vote and tens of thousands of police and soldiers are guarding polling stations amid fears of violence.
Though not expected to get a majority, Golkar, once the political vehicle Suharto, is tipped to secure the most votes.
Polls officially close at 06:00 GMT on Monday. First results are not expected to be announced until 11:00 GMT. Given the size of Indonesia, it may take a day or two before a significant number of votes have been counted.
Monday's results will be followed by a scramble to build coalitions before the July presidential elections. Opinion polls show Megawati has lost the status of frontrunner to lead the world's most populous Muslim nation.
On test is also the popularity of conservative Islamist parties.
Recent opinion polls have put Golkar in advance of Megawati's party. Voters have been found to be yearning for the stability and rapid economic growth of Suharto's 32-year autocratic rule.