I applied to Oxford for the 2011 cycle (as an American student), and it is fairly different.

Oxford works under the tutorial system. There's a set number of courses and subjects, and every course is specific and roughly fixed. This is basically what the U.S. system calls a major, but you don't generally study anything outside of major. Every class you take is within your course. For the course I applied to, every week there's: 10 lectures, 5 hours of practicals (like labs), and at least two tutorials (which are really small, 1-3 person discussions with your course tutor, sort of like preceptorials in the U.S.)

The narrowness of your course of study is both an advantage and a disadvantage, and you usually graduate with a BA/BS in 3 years and a masters in 4 (compared to 4 years/2 years in the US)

You apply to a specific course at a specific college:

- When you make your application, you make it for the one course you want to study. This means that you need to know before you apply, there is no declaring of majors and it's generally pretty hard to change courses.

- Oxford is made up of about 40 colleges. Most colleges offer most courses; the courses are the same at every college, but the tutors are different, and the main differences between colleges are in the culture, location, facilities, tradition + formality, size, funding, events, and number of tourists, etc. People make a big fuss about which college is better, but really its just be one that fits you the best.

- You can only apply to one course at one college. Each college has a fixed number of spots, which is generally pretty small (ex. CompSci only has 2-3 at Balliol College). If you're a good candidate but the college you've applied to is full, they will pool you for the other colleges. You can also make an open application, which means you are up for any college, but this means you'll generally end up at a less popular or attractive college and there are debates as to whether it negatively impacts your application

As far as the practical aspects, there's around 3 steps:

1. You make an application through UCAS (a.k.a Common App for U.K.) For Oxford and Cambridge, this is due October 15th. This includes an essay, a recommendation, and your testing scores. As an American student, you send SAT, SAT II, and AP scores instead (or equivalent). A-Levels are sort of like AP classes over here, but you are limited to typically 3 or 4. The recommendation is the same, but also talks about your suitability for your selected course. The essay is pretty short, but is more like a resume + cover letter than the Common App essay. You talk about your interests, extracurriculars, and reasons for selecting your course along with your qualifications for that course.

2. Sometime in late November/December, you'll hear back on whether or not you were shortlisted. This means that you've passed the first round of applications, and you'll be subsequently invited to interview at your college. The rate for shortlisting is typically above 60% but depends on course, and is based on your UCAS app.

3. You'll interview at your college with the tutors for your course in December. Everybody who is shortlisted for that particular course goes on the same few days. In my experience, this was like a behavioral job interview, where they ask you conceptual and practical questions and want you to describe your thought process as you solve the problem (e.g., "how would you calculate the efficiency of a fridge?"-type questions but also the "how comfortable is that chair?"-kind.) Earlier HN discussion about CS interview questions: http://news.ycombinator.com/item?id=2103161

4. If you do well, you'll receive an offer in late December/January which is either conditional or unconditional. Unconditional = congrats, welcome to Oxford, while conditional = we like you, but we'd like to see you get a 5 on your CompSci AP, etc. Here the rate of acceptance is much lower, but again depends on course and college, and is based heavily on your interview.