Most on-campus recruiting occurs in a concentrated time-frame (typically Fall for full-time, late-Fall and Winter for summer/internships). I do not have a specific breakdown of how firms recruit, but many will do recruiting on a rolling basis as well. Your best bet is to contact your school’s career services office, as well as HR/recruiting contacts that you have at target firms. As mentioned earlier, online consulting applications are not the best way to go.
In normal years, you may still have a shot – certain offices and departments may be looking to meet headcount; yield rates may be lower than anticipated. In today’s economy, that’s a lot tougher.