Microwave propagation through an eleetrie-field-coupled metamaterial lens with a refractive index gradient is experimentally investigated. A gradient in the refractive index of the metamaterial is introduced by continuous tuning of a single parameter in the metamaterial elements. Experimental field maps, acquired in a planar waveguide, demonstrate that the planar gradient index lens can be used to collimate radiation from a line source, thereby forming a beam. © 2007 IEEE.