The expectation that BPhil candidates have a research experience similar to that of a graduate student -- and produce a thesis of the same caliber as a graduate thesis -- is ensured by proper guidance from the student's BPhil thesis advisor. As such, your thesis advisor must have expertise in research and experience in supervising graduate students sufficient for this purpose.
Your BPhil research project must be in one of your majors. You cannot do research outside of your major. And if you have multiple majors, your research project will be in one of your majors. On occasion, you may be able to combine multiple majors in your BPhil project, but given that BPhil projects are modeled after graduate-level work, this rarely happens, and it is not a requirement, nor expected, that students having multiple majors will combine them into their BPhil project.
The faculty member who is your thesis advisor must be affiliated with the major department in which you will be conducting your research -- if the person does not appear on the "faculty page" of your major's website, you cannot use that person as your BPhil mentor without approval from the Department Chair.
Please contact David Hornyak in the University Honors College with any questions about the selection of a BPhil thesis advisor.