Volatile impact of intermittent renewable energy sources (RESs) on the one hand and the uncertainties of loads and market prices, on the other hand, make the bidding strategy of microgrids (MGs) too risky and high-computational problem. To cope with these challenges, the bidding problem of MGs based on a three-stage hybrid stochastic/interval optimization (HSIO) is devised in this study, which provides a trade-off between covering the volatilities by means of the MG potential flexibilities resources or by means of the energy provision from the real-time market (RTM). To tackle the uncertainties of the day-ahead market prices, the cost-effective stochastic programming (SP) is applied to maximize the profit of MG in the day-ahead stage of decision-making. In order to handle the volatilities of RESs production and uncertainties of RTM prices, a flexibility scheme based on the robust and low-computational interval optimization (IO) approach is designed to minimize the balancing cost of MG in the real-time stages. Comprehensive numerical results are provided to compare the effectiveness, robustness, and computational complexity of the proposed model. Results show that the HSIO model takes advantage of the cost-effective solution from the SP model, and the robust solution with computational simplicity from the IO model.