I've done a lot of red oak + poly furniture and floors, and it's always
going to come out "bumpy" like that because red oak is a very open grain
wood. Don't bother trying to "build" poly on it, it's not worth the
effort. If you really want a mirror finish on RO (you don't on stairs)
you need to use a grain filler first (i.e., shellac, filler, shellac,
poly) but that's a lot of work, and poly is the wrong topcoat for a
mirror finish anyway (can't polish it the way you can other top coats).

I've only ever done a mirror finish on red oak once, and it took weeks,
and it wasn't quite a "mirror" anyway:
http://www.delorie.com/wood/desk/photos/img_1986.html