The Greater Brisbane League (GBL) is the largest baseball league in Queensland, covering teams from Brisbane North, Metro, South, West and the Gold Coast from Little League (U13) through to seniors. The competition is managed by the GBL Competition Committee, a volunteer sub-committee of the Baseball Queensland Board elected by the GBL clubs. The day-to-day administration of the competition is conducted by a Competition Administrator.

The 2017/18 season saw the largest number of players participating in GBL baseball on record, with over 1,500 junior and senior players. All GBL Competitions are gender inclusive, with nearly 80 females participating as players this season across age groups and divisions.

The GBL season coincides with Queensland school terms 4 and 1, commencing in spring (October) and finishing before Easter, with a short break over the Christmas period. The season typically runs for around 20 rounds, with the Division 1 competition taking part in a two game series each weekend. Currently, the GBL Competition runs five divisions for seniors, two divisions for Little League (U13), Junior League (U15) and Senior League (U17) and a standalone division for both U20s and masters (35+). Regions within the GBL run competitions for players under the Little League age bracket (ie, rookie ball and T-ball).

The rules of the competition are written in the GBL Bylaws which are set prior to the start of each season. These rules operate in conjunction with the Official Rules of Baseball and, for juniors, the Little League International Rules (“Green Book Rules”).