It was the fourth "Occupy Congress" protest organized by the 25-S movement in the past month, ThinkSpain reported Wednesday.
The group said more than 5,000 people participated in the Tuesday protest, Authorities placed the number of protesters at closer to 2,000.
Police barriers kept the demonstrators from entering the Congress building.
There were no reports of any clashes between police and the crowd.
Lawmakers were able to leave the building without incident after their debate ended.