We're using the Answers Bible Curriculum (ABC) from Answers in Genesis (AIG), the Adult version of course. They have several age group versions as it is designed for Sunday School, which really defines group Bible Study pretty well, just on a different day.
It is a chronological through-the-Bible study program, which at the pace of one lesson per week will get you through the entire Bible in 4 years. However, no one needs to feel too late or that they missed the boat so to speak, as it is fresh material for anyone to join in wherever we happen to be that week. We use take-home study guide booklets, which are free and well organized for group discussion. You are encouraged (but not required) to read the lesson beforehand.
As of April, 2021, we are in the book of Judges, and our current study guides will take us through 1 Samuel.