Big Oven founder Steve Murch had a pretty good feeling that his company's cooking and recipe service would resonate with the iPhone crowd. But even he was surprised at how quickly it took off.

The free application, which allows users to search through 160,000 recipes, this week surpassed one million downloads. That's an impressive number given that Big Oven's application has been in the App store for only three months, and Murch tells me they spent zero dollars marketing it. As noted last week, Big Oven isn't the only Seattle company gaining a massive audience on the iPhone. Restaurant locator Urbanspoon recently surpassed 2.2 million downloads.

A well known Seattle entrepreneur who previously held executive roles at Expedia, Murch shared four reasons why he thought the Big Oven iPhone application was resonating.

1) Massive addressable audience: "BigOven's addressable market is anyone who uses the Internet and cooks (or wants to).  If you own an iPhone or iPod Touch and you cook for the household, I think it's fairly likely that at some point to wander by the iTunes store and type "recipe" to see if there are apps there. (It's interesting to me that we're announcing that BigOven was downloaded 1,000,000 times roughly the same week that Apple Inc. announced 300 million downloads for the entire year. While 1/300th isn't an astonishing share-of-downloads, it's pretty sizeable given how many other apps there are, and the fact that our app was shipped in the fourth quarter.)"

2) Natural fit with mobility: "It solves a real, everyday need: Have you ever been at a grocery store and wondered if you've got everything for that dinner you wanted to prepare? Or been stuck for what to make? Or wondered how to best identify a ripe avocado? We've got dozens of comments back from users that they find it incredibly helpful to look up recipes at the grocery store to double-check that they have everything they need."

3) Natural fit with the iPhone target audience: "As you know, the iPhone is a more "consumer" focused device than, say, RIM's Blackberry, and iPhone owners are often the "chief household officer", where BigOven fits right in. "

4) Best in category and free: The BigOven App is also the only cooking app in the iTunes store that has more than a few hundred recipes (overwhelmingly so -- BigOven has 160,000+). Last I checked, it's really the only free one that has recipe reviews, photos and a food glossary.