We report on a semiconductor-superlattice oscillator with a superlattice electronic device (SLED) containing superlattices connected in parallel and series as active elements for generation of millimetre waves. We present experimental results indicating that parallel connected superlattices can lead, compared to a single superlattice as the active element, to an increase of the output power of the oscillator. Studies of blocks of parallel connected superlattices in series lead us to propose using a SLED with parallel and serially connected superlattices as an active element. Our superlattice oscillator, with different arrangements of superlattice mesas in a quasiplanar design, operated in the frequency range of around 100 GHz. It was electrically tunable and delivered microwave power of about 0.1 mW.