There is so much to do in Corvallis and Oregon in general. I don't want to be a broken record so I am going to add things that I would like to do if I was visiting because many places will give you many of the same recommendations.
Block 15 Brewing Co.
300 Southwest Jefferson Avenue, Corvallis, OR 97333
There are two locations, both are great for different reasons: downtown is often busier and is in and amongst all of the other restaurants and shops. This is the downtown location.
Block 15 Brewery & Tap Room
3415 Southwest Deschutes Street, Corvallis, OR 97333