They joined with firefighters at Columbus Fire Station 1 to voice their opposition of the bill, 10TV's Danielle Elias reported.
If the bill passes, it would dramatically change bargaining rights for state workers, end binding arbitration for police and firefighters and limit bargaining rights for teachers.
Those in favor of the bill said it will increase flexibility for employers and help save the state money.
Ohio is facing an $8 billion budget shortfall.
SLIDESHOW: Images From Protests
Gov. John Kasich has said that he supports the bill.
Those who oppose the bill said they are willing to make concessions but said removing bargaining rights is not the way to fix it, Elias reported.
"Our guys are scared and these are firefighters that are not afraid to run into
burning buildings," said Battalion Chief Jack Reall, who is also president of the firefighters
union. "They're not afraid to start an IV on a baby. These are firefighters who have no fear and
they are afraid right now."
On Wednesday, Senate leaders said that they plan to change the bill, to allow state workers the chance to negotiate wages, but the measure would still ban public employees from striking.
Senate President Tom Niehaus said that the change came after lawmakers considered testimony on the bill. He said he does not view the revisions as a compromise of the bill's intent.
State Sen. Kevin Bacon said the Ohio Department of Administrative Services suggested that keeping some sort of collective bargaining would be more cost-efficient than eliminating the system entirely.
Hearings on the bill have drawn thousands of protesters to the Statehouse and prompted a visit by the Rev. Jesse Jackson.
Any amendments to the bill were to be due by noon on Friday.
Stay with 10TV News and 10TV.com for continuing coverage.