In this work, we develop a computational framework for designing TE alloys by combining first-principles calculations with alloy and point defect modeling. We believe that this is the first computational work within thermoelectrics that simultaneously considers the effects of alloying on the transport properties and doping. We apply this framework to identify specific compositions of n-type Ba 2(1 x) Sr 2x CdP 2 Zintl alloys that optimize the electronic and phonon transport properties, as well as ntype dopability. The computational framework builds upon wellestablished alloy modeling techniques, including special quasirandom structures (SQS) and effective band structure (EBS) to quantify the effect of alloying on the transport properties. To assess the dopability of alloys, we extend a standard approach for computing point defect energetics in ordered structures, akin to our prior work on defect modeling of complex disordered structures. Through the application of this computational framework, we identify Ba 2(1 x) Sr 2x CdP 2 alloy compositions that minimize alloy scattering of electrons, promote conduction band convergence, lower lattice thermal conductivity and are n-type dopable. We validate the predicted crystallographic and disorder properties by synthesizing and characterizing a series of alloy compositions.