Lisa, I haven't sown the bearded, but three other types more than once and have good germination. (foetidissima, chrysographes- my favorite, & sibirica)

What I've found, if I give them a soak of a few hours (not usually necessary for winter sown seeds), sow and leave inside for 2-4 weeks as is suggested for almost all Iris on the Clothiers site, then put them outside in the cold, most of the seeds will germinate in Spring. Keep in mind this is a mild wet Z8 and we have many, many rainy weeks of cool weather well into Spring.

The times I've straight winter sown them and started with cold in Dec or Jan, germination has taken place very sporadically for almost a year, a seed here, then a few weeks later another, about the time I decide to give up on the rest yet another pops up...so I'm hanging onto that seed pot for many months and keeping it watered over summer.

I don't know for sure if the same is true for the bearded types but I don't sow iris any more without keeping the seeds moist and sown at room temp for at least two weeks before exposing to the chill of outside.

I winter-sow the Japanese (Ensata) iris every year and have fairly good germination. Sometimes they take an extra month to germinate though. I love them because the foliage stays beautiful all season. The blooms are short lived though.