Methods for treating tissue, and surgical assemblies and related methods are disclosed in which a single input is used to sequentially articulate two members. A surgical assembly includes an end effector, a base supporting the end effector, an input link movable relative to the base through a range of motion between a first configuration and a second configuration, and an actuation mechanism. The end effector includes a first articulated member and a second articulated member. The actuation mechanism drivingly couples the input link to the first articulated member within a first portion of the range of motion and drivingly coupling the input link with the second articulated member within a second portion of the range of motion so that a movement of the input link from the first configuration to the second configuration articulates the first articulated member and then articulates the second articulated member.