We don't have houses, so our tradition developed because of it.
On pref night, you are told that if you receive a bid the next morning, you are to bring a big zip-up jacket. We have all women who received a bid come to our student center (GC) at 11:00 am the next morning. Women who were not offered a bid were called earlier that morning. Each Rho Gamma group meets up and they go upstairs according to the time that their entire group is present (which makes for some hilarious moments - I was 2 minutes late because of parking and two of my Rho Gamma group members had already tracked down my number from a TKE friend of mine and called me to find out where I was!). They open their bid cards with Campus Life staff and their Rho Gammas and accept or decline. If they decline or are visibly upset, the Rho Gamma and/or Campus Life staff will console and/or counsel the girl.
If they accept, they sign their paperwork and go downstairs to another room to pick up their bid day shirt and change into it. Then, they pick up their big zip up jacket and make sure all of their shirt is covered. Once everyone who has received a bid changes and has their jacket on, they recite the Panhellenic Creed. While they are reciting, the Rho Gammas and Pi Chis change into their chapter jerseys and grab their RG/PX zip-up jackets and meet up the women again, so everyone goes crazy trying to guess what chapters they belong to.
THEN, each group is led down to the ballrooms downstairs. We go downstairs through the back entrance and wait. The chapters have already picked sections of the ballrooms and decorated them with bid day bags, huge wooden letters, etc. So, each group goes onstage, the women count to 3, unzip their jacket and jump offstage to their new chapter!
After the new members have finished, the Rho Gammas and Pi Chis reveal their affiliation and jump off the stage to rejoin their chapter and join in separate bid day festivities.
It's SO much fun, and as a former Pi Chi, it feels amazing to jump off stage and re-join your sisters after a long summer of recruitment madness! Lots of cheering and jumping and hugging ensues.