Asking for Research Position in Person I am an undergraduate student at a university with a strong co-op program. It is assumed and well-known by all the professors that all students will complete one or more co-ops, and that it is currently application season.

I am currently taking a class in a subject manner that is strongly related to my career goals, and the professor has made it well-known to the students in his class that he runs a lab on campus performing research in this area (quantum optics). 

I would like to approach this professor and ask him if he would consider hiring me to perform research in his lab for my co-op. Since I take his class, I know his office hours, and I've visited him during this time already a few times. 
 So far, all the times I've attended his office hours I have been the only student there. Although this is suspicion, I believe he thinks I am strong student, as he allowed me to take the class despite not having a prerequisite after indicating the extent to which I've self-studied the material and discussing previous work experience.

My question is: would it be a bad idea to ask about potential opportunities in his lab in person at his office hours, or would this be better addressed in an email?
In my experience, you are more likely to be noticed by a professor if you actually show up in person. Busy people tend to overlook/ignore/forget emails, and asking in person makes more of an impression. Since you mentioned attending his office hours, your face might seem familiar, while your name might not (you did not mention mailing him explicitely).

Before asking, think about what skills you can bring to the table (he might ask you about programming languages etc).

Do not, however, overstay your welcome: it is likely he will not hand you a contract right on the spot, but maybe wants to ask around his department/think of a task to give you first. 

In any case, make sure to tell him your full name and/or email address, he might want to write it down ;)