Do wardrobe departments at tv and movie studios provide undergarments as well as clothing to actors ?

99.9% of the time they will, if what they're wearing is considered wrong for the scene (e.g. white "granny panties" with low-cut jeans where they're supposed to appear sexy, etc.), or if they're not wearing undergarments and / or the scene calls for a specific "look" which would include the undies (e.g. boxers instead of briefs; scenes with lingerie, etc.)... but yeah, they normally provide everything. Interesting question though, as most people tend not to think about that.

Here's a good article from someone in the industry that talks about this exact issue:

http://stumpedmagazine.com/articles/underwear-ques...

Hope that helps :)