Hello - sorry I didn't reply to this earlier, I haven't wandered onto this thread for a while.
In many ways I imagine Brasenose and Oriel as quite similar - they are both small, central, old etc. But obviously I love Oriel, so I'm hideously biased. In answer to your priorities list:
- Smallish: Oriel is pretty small in terms of student numbers. There are about 90 people in each year, which means you get to know everyone. But you also get to know people in the years above and below you, so you're not just restricted to your age group.
- Really sociable and friendly: definitely a massive 'yes' as far as I can tell. Everyone is able to live on the main college site for the first two years (and about 1/3 or so of the third years do too, whilst everyone else lives in a nice annexe about 15 minutes away on Cowley Road) so you will get to know all the people around you very well, perhaps better than you would like at times

All colleges say they are 'friendly', and this is true, but most colleges seem to make 2nd years live out in annexes and finalists (3rd years) get to live on site. Oriel has 1st and 2nd years living on the main site, so there is a lot more mixing between the year groups, whilst 3rd years get to stress away from the hustle and bustle of all the fun that is being had.
- Good bar: probably not the cheapest in Oxford but everyone hangs out there, plays pool, darts, quiz machine etc. You can charge non-alcoholic drinks and food/sweets to your termly account, so you don't have to pay upfront for some stuff.
- Rah/rugby boys: there are some rahs and rugby boys but not in the way that they are at school i.e. a clique on the edge looking down their noses at everyone. Anyone who talks about their 'gap yah' gets the mickey taken out of them a lot - the Gap Yah sketch was written and performed by Oriel people. Oxford in general isn't exactly a rah-free zone, but it's honesty nothing to stress about.
- Drama: lots of people in college get involved in drama. The Oriel Lions provides funding to support a lot of student plays and normally puts on some sort of play every summer term. It varies from year to year, depending on the interests of each intake, but there are plenty of people in years above willing to help you in the right direction. We had a really strong showing in the freshers inter-collegiate (Cuppers) drama competition this year. The college also has a fairly strong tradition in the Oxford Revue comedy group in recent years.
- Not too intensively hard-working: The college is making a bit more of an effort to move up in the Norrington Table after being at the bottom for absolutely ages but the student emphasis is very much on working hard, playing harder. We have great bops (college parties) that are really well-attended throughout the year and by all year groups, where everyone makes a big effort to dress up. In general, big groups get together and go out regularly during the week and there is virtually always someone in the bar that you can chat to. Being a small college, everyone gets encouraged to do some kind of college sport, whatever their ability. When it comes to exam time, people knuckle down and word hard, but we're not obsessed with getting firsts all of the time.
- Vegetarian food: I won't lie, it's not amazing. The food is better for non-veggies but one of my best friends is a vegetarian and she gets on fine. You quickly learn to pick out the stuff that is good from the menus and we have several kitchens scattered around the main site that you can use to cook for yourself. Food in hall is provided on a pay-as-you-go basis, so you won't have to commit to eating in hall in advance and can go as often or as little as you like.
Sorry, that was very waffly but hope it was of some use.