[ifspuds]

You should take a look at the sticky thread at the top of this forum. There are tons of premade schedules there, many with interleague play. They're very simple to use, just download them to your OOTP6 folder, go to league setup and edit schedule and hit the CSV import schedule button.

If the format (# of teams, # of divisions, # of interleague games, etc.) you want for your league isn't there, then yeah, I think you'll either have to Stickware it or create your own.