The jet-cooled laser induced fluorescence spectrum of the (B) over tilde <- <(X)over tilde> electronic transition of 2-methylvinoxy radical is assigned as a superposition of contributions from noninteracting cis and trans isomers. The spectrum of the cis isomer is identified by comparison with ab initio electronic structure calculations; both theory and experiment clearly indicate that the methyl conformation changes from the (X) over tilde state to the (B) over tilde state. Fits of both hot and cold bands to a one-dimensional torsional model yield methyl rotor barrier magnitudes of 270 +/- 20 cm(-1) in the (X) over tilde state and 200 +/- 20 cm(-1) in the (B) over tilde state. The ab initio calculations show that in the ground state the preferred conformation places one methyl CH bond in the plane of the molecular frame cis to the vicinal CC bond. Assignment of the spectrum of trans-2-methylvinoxy is more tentative because no resolved hot bands are available to corroborate the model. Our best estimate for the (B) over tilde state barrier magnitude is 60 +/- 15 cm(-1). Multireference configuration interaction calculations and coupled cluster calculations are reasonably successful in obtaining methyl torsional barriers in agreement with experiment, although high accuracy is elusive for the B state of both cis and trans isomers. By comparison with simpler cases, we infer that the Jr radical character of the B state strongly influences the methyl torsional barrier.