While U.S. Senators held a marathon voting session to take down Obamacare, they were more than happy to spend freely on pizza, after pizza after pizza ... and tons of wings too.

Sources inside the historic vote tell TMZ ... the Senate ordered out to We, The Pizza around 20 times throughout the night. We're told the average order was 7 pies covering the gamut -- supreme, pepperoni, sausage, veggie and just plain old cheese. They also inhaled at least 200 wings.

The delivery guys made out with much higher tips than usual. One driver even walked away with a hundo for a single delivery. We're told the Senate dropped about $5,000 for the evening's grub.

At least they were eating healthy while dismantling the Affordable Care Act. The vote moves to the House next -- so, maybe Chick-fil-A to go?