In this paper we study an actual problem proposed by an agricultural cooperative devoted to harvesting corn and grass. The cooperative uses harvesters for harvesting the crop and trucks for carrying it from the smallholdings to the landowners’ silos. The goal is to minimize the total working time of the machinery. Therefore, the cooperative needs to plan both the harvesters and trucks routing. This routing problem simultaneously incorporates the following characteristics: time windows, nested decisions, processing times required to service each facility and the fact that facilities must be visited in clusters. A binary integer linear programming model is proposed to solve this problem. However, since approaches dealing directly with such formulation lead to considerable computation times, we propose a heuristic alternative solution approach for the problem. The heuristic is applied to the case of the cooperative “Os Irmandiños” with a large number of landowners and smallholdings. We report on extensive computational tests to show that the proposed heuristic approach can solve large problems effectively in reasonable computing time.