In any instance where the governing party is reduced to a minority (or is elected to another minority), the other parties always have the option of voting them out of office on the speech from the throne. They mostly don't, whether because the opposition parties don't agree or else they consider it politically inopportune to do so. But it does happen. That's what David Peterson and Bob Rae did in Ontario in 1985, leading to Peterson's Liberals taking office with the backing of the Rae New Democrats.
King's government in 1925 did pass a speech from the throne at the beginning of the session. They'd been running the House of Commons for several months before they were defeated on a confidence matter -- hence, why King believed he deserved a dissolution. Had he been defeated right out of the gate, there'd have been no question that Meighen was entitled to attempt to form a government.
Thing is, when faced with foes in the legislature that outnumber you and with the power and intent to compel your resignation, most minority governments will not even attempt to stay, and resign without the need for conflict.
I was looking at Harper's Cabinet, guessing at who is in danger of being defeated, since Joe Oliver is clearly the highest-profile example. Amongst the full ministers, I counted Oliver, Leona Aglukkaq (Nunavut), Gail Shea (Egmont), Kerry-Lynne Findlay (Delta), Greg Rickford (Kenora), Chris Alexander (Ajax), and Bernard Valcourt (Madawaska-Restigouche) as the most likely to go.