The recent policy changes in the energy sector encourage wider investment in microgrids (MG) having a high proportion of renewable energy and their integration into distribution systems (DS). MGs are expected to complement the DS technical and economic operation; however, their power purchase agreement (PPA) can increase the energy bills of the DS customers. The onus of this study is to investigate the impact of multiple MGs on the DS operation where the MG investors are offered different power purchase contract options. A two-phase methodology is developed to solve the operation interactions of the DS operator (DSO) and MG owners. In the first phase, the optimal sizing of the MGs is determined considering a coordinated integration approach for the MG owners. In the second phase, the yearly co-operation of the DSO and MGs is analyzed considering the yearly load profile and deviation in the capacity factor of the respective MGs. Simulations are carried out on a modified IEEE 33-Bus System consisting of a DSO and three MGs. Relevant results and suggestions are provided for the effective inclusion of the MGs in the DS.