We present calculations of certain limits of scheme-independent series expansions for the anomalous dimensions of gauge-invariant fermion bilinear operators and for the derivative of the beta function at an infrared fixed point in SU($N_c$) gauge theories with fermions transforming according to two different representations. We first study a theory with $N_f$ fermions in the fundamental representation and $N_{f}$ fermions in the adjoint or symmetric or antisymmetric rank-2 tensor representation, in the limit $N_c to infty$, $N_f to infty$ with $N_f/N_c$ fixed and finite. We then study the $N_c to infty$ limit of a theory with fermions in the adjoint and rank-2 symmetric or antisymmetric tensor representations.