See
http://oregonstate.edu/cw_tools/cam...terY=1858&pBN=&BN=Pharmacy+Building&L[]=6&Z=4
After you get off I-5, follow the signs to OSU Main Campus (not the stadium) and you'll eventually wind up on Jefferson Street. There will be a little information booth on the right side just before you get into campus, and they should be very helpful.
But in case they're not, there is a large area of parking around the corner of 15th St and Washington Ave which I think is your best bet that's close to the Pharmacy Building, about a 3 minute walk. It's fairly full, but I don't think it's ever been completely full, except during football games. There's a pay station in the middle by Washington (purple star on the lower right of the map above), and it's $1 per hour or $5 for the whole day.
If that's full, the parking structure is actually finished now, and there's plenty of space there, but it'll be a 10 minute walk. There's no pay station there, so you'll still have to go get a permit. Lastly, there's free parking available at the gravel lot (not the paved areas) at the stadium, so you would follow the signs to the OSU Reser Stadium instead of the Main Campus. There's a free OSU shuttle that will take you from there to where you need to go. Just wait for the East shuttle (they should come around every 15 minutes) and tell the driver you need to get to the Pharmacy Building. They'll let you off across from the big 6 story Valley Library, and if you walk halfway towards the clock tower, you'll see a building that says 'Pharmacy' to your right.
I'll bet this was way too much info for you, huh? Just shows how bored I am with studying. Good luck at your interview!