Brunch in Providence, RI near the Biltmore Hotel
I'm going to watch this post myself because I just can't think of any really great spots.
Downcity Diner is within walking. It's a fun place with good atmosphere that could most likely take a group since they have an upstairs too. In my opinion the food is fine-to-good but can be inconsistent.
We ate at Citron when it first opened and it was "eh"... like a place that really does dinner but happens to be open for brunch, you know? Maybe you can find a recent posting or someone to chime in, perhaps they have improved.
I really generally despise chains but Joe's at the mall (gasp!) could most definitely take a group and I personally like the atmosphere. The food is very good but it's not "great" as you request.