We report the rotational analyses of six bands of the (B) over tilde - (X) over tilde electronic transition of jet-cooled I-butoxy radical and I I bands of the corresponding transition in I-pentoxy radical. From these spectra, we have obtained experimental values for the rotational and spin-rotational constants in the (X) over tilde state and the rotational constants, vibrational frequencies, and band origins in the (B) over tilde state. By comparing the rotational and spin-rotational constants from these analyses with corresponding values from quantum chemistry computations, we assign the observed spectra to the electronic origins and excited vibrational levels of the (B) over tilde state of three distinct conformers of 1-butoxy and five distinct conformers of I-pentoxy. These assigned bands can be used as unambiguous diagnostics of the radical species, its structural isomer, and its conformation. These data can be used to identify, and to some extent rationalize, distinctively different conformer stabilities in the (X) over tilde and (B) over tilde states and conformer-dependent dynamical behavior.