Moreau, 55, is the second person to present an official candidacy to replace former premier and party leader Jean Charest.
He was supported by nine other Liberal MNAs.
Former finance minister Raymond Bachand confirmed his spot in the race on Sept. 28.
Former health minister Philippe Couillard is expected to make his own announcement on Tuesday or Wednesday in Montreal.
Moreau was elected to the assembly for the first time in 2003, but he was was defeated in 2007.
Between 2007 and 2009, he acted as chief of cabinet for the parliament leader. He did, however, get re-elected as an MNA in 2008 and 2012.
Some say Moreau's age makes him a member of a "new generation" of Liberals.