Hi .. using Opera 26 and came here looking for the same info: "Where the heck is Bing as a default??"

Just sharing my little workaround, which seems to work well. Went to Bing homepage. Right-clicked inside their search box. Chose Create Search Engine. Added the Engine, with the one-letter shortcut "b". Now, when I hope into the Address Bar, I just type "b [whatever search terms]" and it takes me to my Bing results. So with the typing of one extra letter, you get Bing as your default.

Hah -- don't really understand WHY it works. After all, you can make a Bing shortcut in Opera as an added engine, but this way it also sends your query along for the ride, rather than typing "b" and THEN doing the Bing search.

Not sure if this quite what people want but just tossing it out there. I've JUST started using Opera, so I'm sure more experienced Opera users are already doing this. Cheers...