Well it depends on where you want to be. Oktoberfest to many homebrewers today means a lighter colored brew which is essentially a bumped-up Munich Helles recipe usually made with a blend of Vienna and Pils malt. Personally I prefer an older style which is a darker beer based on dark German Munich malt.
"Modern" Festbier 5 Gal US
5.5# German Vienna malt
3.5# German Pils malt
.75 oz Hallertauer 4.5% AA @ 60 min
.25% Hallertauer 4.5%AA @ 20 min
WLP 830
"Traditional" Marzen/Oktoberfest
7# German Dark Munich malt
4# German Pils malt
.75 oz Spalt Spalter 4.75% AA @ 60 min
.25 oz Spalt Spalter 4.75% AA @ 20 min
WLP 838