"Wall Street, the banks and the Fortune 500 now run this Republic," he added.
The AP reports the crowd "roared in approval" when Moore called on them to keep pressuring Gov. Scott Walker (R) to drop his proposal to end collective bargaining for thousands of state workers in Wisconsin. Moore also compared the struggles in Madison "to Egypt's revolt."
Moore tweeted from the rally, which was streamed live on his website.
"2 things I saw in the crowd in Madison: The thousands of teenagers & the thousands of ppl in their 70s & 80s! Most diverse demo I've been 2," he wrote.
The protest was the third "mega rally" of the Madison standoff so far.
Others addressed the crowd as well, including Rep. Tammy Baldwin (D), who represents Madison in Congress. State Sen. Chris Larson, who's among the 14 Democrats who've skipped town to shut down Walker's so-called "budget repair bill," sent word according to the AP and "urged protestors to stay strong."
"We've been here for the last 16 days we'll continue to be here until worker's rights are removed as the target in this budget repair bill by our governor," he said.
Reports say nearly 4,000 were inside the Capitol today. Official estimates of the crowd outside are not yet available.
Watch Moore's speech:
This post has been updated.