For all you part timers, I suggest you look up your state's laws regarding breaks. It might even be posted in your hub/center, along with the federal laws about minimum wage, nondiscrimination, right to organize, etc.
For example, Illinois law provides for a 20 minute unpaid break; it's in the IL ODRISA (One Day Rest In Seven Act), which also means you don't have to work every day of the week in Illinois. The last couple of years I was on the preload shift starting as early as 11 PM, many of us had no problems taking our unpaid meal breaks; just kept track of our hours, and our FT supe was really good about making sure our timecards were accurate.
Some of the people I work with says that last peak, the supes screwed everybody out of overtime by making them take an hour break in between double shifts to make it seem like they were working two separate shifts instead of a full 8-9 hours
Did anyone read your your contract supplement about overtime? In some areas, if part timers work over 8 (normal, non-peak double shifting), they only get premium pay after 8. Also, was the unpaid hour break negotiated with the local union? If not was a grievance filed?