Hi! I was just as excited as you last year and also scoured this forum for details on o week . I don't think plans for this year's orientation have been fully finalized yet, but I can tell you what happened last year.
The first day was a marathon - we had to arrive at Osgoode at 8am and the events of the day didn't finish until around 8:30pm. During the day, we toured the school, sat in a presentation or two in the moot court, went to old Osgoode to tour around and take a group photo, and then went to a bar near old Osgoode where they provided some much needed food. The old Osgoode tour was unessecary and tiring and I hope they get rid of it this year. Day 1 really isn't formal at all - just wear something comfy and know that you will be getting an orientation tshirt to put on once you get to the school. I'd also recommend bringing a backpack, a waterbottle, and a snack because the day is SO long and you'll be given this big awkward tote bag of goodies from firms and it's nice to be able to put it in your backpack instead of lugging it around.
I can't remember the exact schedule, but I think day 2 was a beach volleyball and board game day. Once again, it's super informal and you have to wear your orientation shirt. That night we had the boat cruise on Toronto harbour - which is amazing. For us, the dress code was semi formal black and white and there was a big variety of formality amongst the group. Most women wore short or midlength dresses and men mostly wore dress shirts and pants. After the boat cruise everyone heads to a bar and people generally got pretty drunk.
I think day 3 was an event on Toronto island. Once again, 1Ls were expected to wear there orientation shirts. I didn't go to this because I was too hungover from the boat cruise.
There was also an optional blue jays game and ROM tour that I didn't go to.
There are a lot of drinking events. One night there was karaoke In the JCR (the student bar at Osgoode), and there was also a pub crawl of the Church/Wellesley area.
On the last night there is the "Deans Gala", which is the most formal event of the week. Once again, there was a lot of variety in clothing. I found that women wore a lot more full length dresses than they did on the boat cruise but it was still probably at least half short dresses. I think the men wore suits. At this event, the "winner" of O week is announced and members of each section win awards for being "most spirited".
O-week is a competition between the 4 1L sections to win O-week, and all week there are competitions to earn "points" for your section (e.g. At beach volleyball, karaoke). Throughout O-week and during the time we were taking ELGC we had to attend almost daily "dance practices" where our orientation leaders taught our section this choreographed dance. All the sections perform their dance at the Dean's Gala and it's worth the most points in the competition.
If you want a more detailed breakdown of the timeline just let me know. I was too lazy to dig up my old o-week schedule, but you can probably access it online. Congrats on getting into Osgoode and I will see you this fall!