What kind of shirts are good for "office casual?"?

I am going to a conference where the dress code is "office casual." Can I wear cotton knit shirts with no collar? (T-shirt material, but they are fitted, not baggy, and they have lace or crochet at the neck). At the school where I work, I'm not allowed to wear them - we have a no t-shirt rule - but would they be ok for most other office casual settings?