We report the infrared charge dynamics of YbIn1-xAgxCu4 in a series of x- and T-dependent reflectivity measurements. Within the low-temperature coherent phase, characteristics of a low energy (0.25 eV) excitation appear to be controlled by the same Kondo scale, TK, which is relevant to the magnetic response (Phys. Rev. B 56 (1997) 7993). We show that the observed TK dependence of the frequency and strength of this excitation is consistent with an interpretation in terms of a coherent-to-incoherent quasiparticle transition between the correlation-induced bands of the periodic Anderson model (Phys. Rev. Lett. 92 (2004) 186405). Additionally, we consider an interpretation of x-dependence in the higher frequency optical response in terms of a rigid band structure picture where the filling is depleted by Ag doping, augmented by a Kondo resonance which tracks the x-dependent Fermi level. In addition to the properties of the low-temperature phase, our results also encompass the anomalous temperature dependent behavior in the vicinity of the electronic phase transition at low doping (x<0.3). © 2005 Elsevier B.V. All rights reserved.