The OAS was a right-wing terrorist organization devoted to maintaining settler rule over Algeria. It did this by a campaign of bombing, terror and assassination, against the Algerians on one hand and pro-independence French on the other. They failed -- Algerian independence was inevitable, and arrived within 18 months. But while failing, they managed to utterly poison relations between settlers and Algerians.
Okay, so [handwave] say French security services get the drop on the embryonic OAS in early 1961. Or, failing that, have the leadership blown to pieces by a convenient bomb. Whatever -- no OAS.
Now what?
Well, there's probably no Massacre of Oran. So there might not be a mass flight of settlers after independence. OTL, out of about 1.4 million settlers, all but 100,000 or so fled, most going back to France. TTL, we might see a lot more settlers staying behind. How many is a reasonable question, but the experience of _colonates_ elsewhere in Africa suggests that half might stay. That's over half a million -- enough to still have a big influence on the subsequent development of Algeria.
The optimistic view would be a richer, slightly more liberal multicultural Algeria. (N.B., this seems optimistic but not completely daft.) The pessimistic view... well, there are plenty of ways this could go bad. Still, it would be starting from a much better point than OTL Algeria.
There are probably also complex knock-ons on internal French politics, but I'm not really competent to judge those.
Thoughts?
Doug M.