The emergence of the Gas Exporting Countries forum as the main player in the global gas market gives a special importance to the analysis of the changes in the behavior of the members of this forum including Iran and Qatar, due to the competition in the extraction of the South Pars-North Gonbad joint gas field. In this article Iran and Qatar’s behavior in the Gas Exporting Countries forum has been analyzed by using Markov switching model and monthly data from 2008 to 2022. The results showed that the Qatar’s behavior pattern does not fluctuate between collusion and competition regimes over time, so that Qatar's behavior in both regimes has been non-competitive and based on the pattern of "partial market sharing".

But the Iran’s behavior pattern does fluctuate between collusion and competition regimes over time, so that Iran's behavior in the first regime has been competitive and the Second regime it's behavior has been non-competitive based on the pattern of "partial market sharing". This means that Iran's behavior in the Gas Exporting Countries Forum during the period under review has changed. In fact, Iran and Qatar in the Gas Exporting Countries Forum haven't had common role with Saudi Arabia in opec as pattern of " market sharing and Making price". The results also showed that the Iran and Qatar’s average stay length in the first regime is 22/33 and 21/93 months and the average stay length of these two countries in the second one is 18/11 and 11/02 months respectively.