Lawmakers reappointed President Jalal Talabani, a Kurd, who renamed incumbent Nouri al-Maliki, a Shiite, as prime minister, The Washington Post reported Friday.
Osama al-Nujaifi, a member of the Sunni-backed Iraqiya bloc, was elected Parliament speaker.
With the three top spots filled, Maliki can begin filling ministry posts, which observers said could be another contentious exercise.
The milestone, reached Thursday, came a day after a power-sharing pact among Iraq's major political factions, the Post reported.
Members of the Iraqiya bloc said they walked out of negotiations to protest suspicious tactics by their political rivals and broken promises to repeal a controversial law they said targeted their members unfairly, the Post said. The Iraqiya bloc won more seats in Iraq's 325-member Parliament than any other bloc in the March elections.
"They have to know that they cannot run the Parliament the way they want," Iraqiya lawmaker Falah al Naqib said. "There is no trust. The political process is very fragile. You can see that there are major differences. They should at least respect their promises."
Despite the drama, U.S. officials said the election of an Iraqiya speaker and a Kurdish president were the desired outcomes, the Post said. U.S. officials advocated a power-sharing system of governance.