Is it possible to change majors at UC's?

Let’s say I apply as a history major at a UC, then decide that I don’t want to do it anymore and want to do some engineering major. What , if possible is the latest to make this change?

As a Freshman or Transfer?

Switching from a less competitive major i.e. History to a more competitive major like Engineering is very difficult at most of the UC’s. Some UC’s like UCSD, unless you are a direct admit, you will probably never have a chance to change. UCSC/UCR and some Engineering majors at UCD can be changed into after meeting a specific GPA and taking some pre-req courses. If Engineering is your choice major, I suggest you select that option on the application. Always easier to move down to a less competitive major than up.

Since Engineering majors have a lot of pre-req and major classes (unit heavy), switching as early as possible would be to your benefit.

I would also pay attention to which schools will allow you to enroll in the Engineering pre-req classes. Some of the UCs we visited made it very difficult to get into Bio, Chem, Physics, etc. if it wasn’t a requirement for you major (which it wouldn’t be for History). UCSB and UCD were the exceptions however UCSB said that if you aren’t accepted into Engineering initially, there is an extremely low likelihood that you will be able to transfer in.

UCSB does have a very large College of Letters and Science which includes everything from History to Physics. Within the College of L&S, you can enroll in whatever classes have openings regardless of your major.

sure you can - but, the process varies by campus and major.