This paper presents a method for controlling an omnidirectional vehicle with multiple modular steerable drive wheels. Each wheel module has two independent drive wheels and a two-degree-of-freedom (2DOF) attachment consisting of an active prismatic joint and a free rotary joint. The attachment enables the wheel module under nonholonomic constraint to move the chassis better omnidirectionally. A controller consisting of vehicle-level and wheel-module controllers is designed to coordinate wheel modules to ensure correct vehicle movement. The vehicle-level controller determines the desired acceleration of the vehicle chassis to track its reference path, and each wheel-module controller controls its own actuator movement to generate the desired acceleration. If the prismatic joint on the wheel module approaches its mechanical limit, the vehicle-level controller corrects the acceleration to keep the joint position within the workspace. Simulation of a vehicle with four wheel modules confirmed the effectiveness of the proposed control.