The legislation does not give specific time frames for frequency of meetings.  The OHS Regulation 2001 (Clause 22) provides the following information:

The employer must consult their employees about arrangements for OHS committee meetings including:

• the frequency of ordinary meetings and special meetings;
• the procedures for any meetings including whether they may be held by electronic communication or the circulation of papers.

The OHS committee should meet frequently enough to enable meaningful input into decisions that relate to OHS matters.

Consideration should be given to the hazardous nature of the workplace when determining the frequency of meetings.  If the potential for injury is high, more frequent meetings may be required to discuss ongoing prevention strategies.