MORAGA -- Rodney Mattos had never been to a Saint Mary's College post-commencement "plot party" before Saturday.
Standing beneath one of dozens of shade canopies that dotted the chapel lawn, within arm's reach of a stocked bar and overloaded buffet table, a nearby ice sculpture in the form of the school's logo sweating in the heat, he admitted he wouldn't mind trying another. And another after that.
"This is the first time I've experienced anything like this," said Mattos, whose son Rodney Mattos Jr. graduated with a degree in finance. The elder Mattos has an 18-year-old son and 16-year-old daughter. "We're hoping to make it a tradition."
Plot parties, family celebrations that follow the school's annual commencement ceremony in the soccer stadium, is a tradition on the bucolic Saint Mary's campus dating back to the 1970s.
"In those days, there was a party here and a party there," said Michael Beseda, class of 1979, who is now the school's vice president of college communications. "Then it just exploded."
These days the school holds a lottery to dole out the party parcels on the popular chapel lawn. Plots cost from $100 (for groups of 1 to 2) to $315 (for groups of 7 to 12) -- money the school uses to defray related logistical expenses. Insurance is required, as is a signed form pledging alcohol responsibility.
To help families plan their party, the school invites them to meet with caterers and rental companies at an on-campus event.
The Mattos family shared their plot with nine other 2012 graduates and their families. Rodney Mattos estimated it took 2½ months to plan the party.
"For our first attempt, it came out pretty decent," he said.
Greg Brophy attended his first plot party after his graduation from Saint Mary's in 2007. On Saturday, he celebrated, along with what he estimated to be 150 family members and friends, the graduation of his brother, Chris.
"You find a friend who you know is graduating, or a friend of a friend," Greg said from beneath a canopy on a lawn near the rugby field. "It's one of those things where everybody is always welcome. I'm sure Chris saw what I was doing here and was like, 'Why wouldn't I want this for myself?' "
Chris did exactly that.
"I wanted to have one of those," he said of his brother's plot party. "I went to the next three until this one. And I always had a good time."
Not every party was catered -- one featured a full pig roasted in a spit. Some were held beneath market umbrellas in quieter corners of the campus. Adjacent to Justin Hall, a band played while children frolicked in a sand volleyball court. The music wafted over De La Salle Hall and echoed in its courtyard, where a half-dozen groups were spread out across the lawn.
Beseda has yet to hear of another school with such a tradition.
"You'd think there would be another place that does something like this," he said. "But I've never had anyone say to me, 'This other college does it.' It's just this place."
"I have a lot of friends who went to party schools -- ASU, Chico, San Diego State," Greg Brophy said. "They come here and they're like, 'What is this? Saint Mary's gets this? We had nothing like this, and we're the party school. This is awesome.'"
Contact Gary Peterson at 925-952-5053. Follow him at Twitter.com/garyscribe.