Gee. And I thought *I* looked at booking flights a long time in advance.

I can't answer the specifics but I do this sort of thing all the time. (I have an SQ flight coming up with CPH to ARN on SAS, and an AC flight also with the Scandinavian leg with SAS.)

I'd suggest searching your local carrier websites. I assume you're a *A flyer so search United or Air Canada. Lufthansa has a lot of options as well. Turkish Airlines involves a bit of doubling back but they have a lot of flights to Stockholm and I presume Oslo as well. I often start my search on Kayak.com, tick the box for no booking sites (Airlines only) then click through the the actual airline that has the options you are interested in.

If SAS joins Skyteam by then at least you only lose points for a very short hop.

Also Oslo isn't far from Stockholm so you may want a Stockholm return and add a short hop from Oslo back to Stockholm - maybe add an extra night or two there.