Beware the Ides of Märzen
Or don't beware, that's cool too.
Amber lager is delicious, whether you call it Oktoberfest or Märzen .
Before it became a by-the-liter liquid party fuel this, Bavarian beer was called Märzen - the last brew of the pre-industrial, pre-refrigeration brewing season, before the microbially-rich air of the summer months made low-fi wort cooling a risky proposition. March = März in German, hence Märzenbier - "March Beer" - lagered in caves, and busted out as needed during the warm months, and a big kill the keg party at harvest (the same tradition lives in the Bieres de Mars of farmhouse brewers).
So how can a homebrewer make a regulation, export-strength, orange-n-malty Oktoberfest into an old-school Märzen? It's both easy and difficult: brew and ferment the beer now (the easy part), and then store it cold until September (not drinking it early is the difficult part). Yes - brew now for stein-hoisting in another 5 or 6 months. Those who fail to plan plan to fail, as my middle school gym teacher was fond of saying.
One of the most-asked questions we get about Oktoberfest/Märzens comes from homebrewers who don't have the right conditions or gear for long-term lagering at that time of year - can I use an ale yeast? The answer is yes, of course you can, this is your beer. Keep the rest of the recipe intact and swap out the lager yeast. It's not going to turn out quite the same as if fermented with a lager strain, but it will be very good.
Best results can be had if you can keep it cool (under 65 F), and my personal picks are White Labs 029 and Wyeast 1056. Other strains (your California lagers and European ales) would be good choices as well, and our friends in the lab over at Wyeast have reported success brewing lager-styles with their 2124 Bohemian strain at temps into the 60s.
Now, gehen und brauen etwas!