Control of collective pitching for large wind turbines is considered. This paper introduces two main contributions: 1) the design of explicit model predictive control with time varying constraints on boundaries of and limits on the rate of change of the control action and 2) the application of the developed explicit model predictive control for the collective pitch control in large wind turbines. The proposed collective pitch controller acts in region three (i.e. speeds above the rated wind speed) to maintain the turbine's speed and power at their rated values respecting the constraints on the pitch angle limit and rate. The proposed controller is coupled with a PI controller for individual pitch control so as to reduce the moments on the turbine's blades. The performance of the proposed controller is compared to a gain-scheduled PI controller. Simulation results, based on a typical 5-MW offshore wind turbine, prove the merits of the proposed explicit model predictive controller.