The Wildcats, with senior Samuel Ellison covering the anchor leg in 1:46.58, held off runner-up Penn State (7:18.99) and Georgetown (7:19.27) for their first 4x800 crown since 1992.
"To a certain extent, you want to treat every race the same," Ellison said. "But there's nothing like the Penn Relays, as cliche as that sounds. There's something about the atmosphere, something about the people, something about the fans."
Setting up Ellison with a semi-comfortable lead were Josh Lampron (1:51.80), Dusty Solis (1:49.45), and Jordan Williamsz (1:48.77).
"I'm really proud of these guys," O'Sullivan said. "This means a lot to me, so much that you could never even imagine. This is kind of our local turf. So we are under a lot of pressure when we run here. For them to step it up today really means an awful lot."
The 6-foot-5, 180-pound Ellison started his career at Upper Dublin High playing basketball and soccer. The 21-year-old from Dresher switched to track and field as a sophomore, eventually starring in the 800.
Ellison, who is majoring in communications and political science, was recently awarded a William Fulbright Scholarship. He will study social policy at the University of Birmingham in England.
A crowd of 49,103 watched the finale of the 120th edition of the carnival, which was marked by continued relay dominance by Villanova's women.
The Wildcats' 4x800 was made up of Kelsey Margey (2:06.33), Angel Piccirillo (2:06.00), Nicky Akande (2:05.67), and Emily Lipari (2:03.50). The same group won last year in a collegiate-record time of 8:17.45.
Lipari, who also anchored the victorious distance medley and 4x1500 relays, held off a come-from-behind bid by Oregon (8:22.54). Last year, Lipari overtook the Ducks' Laura Roesler in the final 80 meters for a hard-earned triumph.
"I know that Laura is a very competitive person and that she was looking to do the same thing to me that I did to her last year," Lipari said. "I didn't want to give her an opportunity to edge me out on the line, so I took off with everything I had left in the tank with 200 meters to go."
Of repeating in the 4x800, Procaccio said: "I didn't think lightning would strike twice. I told them to try to channel last year. We had nothing to lose and everything to gain."
Eagles coach Chip Kelly, who spent four years at Oregon, was on hand to watch the Ducks easily win the men's 4-by-mile Championship of America in 16:09.67. Stanford (16:17.83) was a distant runner-up.
In gaining his fifth Penn Relays win with Oregon, senior Mac Fleet ran an anchor leg of 4:00.4. "I just wanted to maintain the hard work everyone else put in," the San Diego native said. "My teammates gave me a five-second lead."
Other Championship of America races saw Pittsburgh clinching the men's 4x400 in 3:03.44 and Kingston, Jamaica's University of Technology satisfying a large group of fans by taking the men's 4x200 in 1:20.07.