In this paper we develop the existence theory for a class of nonlinear, infinite demensional optimal control problems, with a priori feedback. This is achieved with the help of property (Q) of Cesari. First we provide verifiable conditions on the data, which guarantee the validity of property (Q). Then we prove two results on the nonemptiness of the set of admissible pairs. This is done by solving an appropriate evolution inclusion of the subdifferential type. Subsequently, we use the reduction technique to prove the existence of optimal pairs. Finally we work in detail four examples illustrating the applicability of our work. These examples include systems governed by both ordinary and partial differential equations.