A powered wheel assembly, and method and ground-engaging vehicle (e.g., a robotic vehicle) using the same, are provided. The vehicle incorporates at least one of the wheel assemblies on its chassis body. In addition to its ability to propel the vehicle across a surface, the wheel assembly is reconfigurable between a retracted configuration, wherein the wheel assembly has a first rolling diameter, and an expanded configuration, wherein the wheel assembly has a second rolling diameter greater than the first rolling diameter. A drive motor assembly may both rotate the wheel assembly, e.g., propel the vehicle across a surface, and selectively actuate the wheel assembly from the first rolling diameter to the second rolling diameter, or to any intermediate rolling diameter.