We seek to investigate the location of the gamma-ray emission zone through monitoring the optical continuum and broad emission lines in a sample of blazars showing prominent and variable gamma-ray emission. These observations will complement the on-going monitoring of their radio (VLBA) and high-energy emissions (Swift; Fermi). The joint information will be used to study the connection between the jet, broad-line region and gamma-ray in order to construct emission maps allowing us to reconstruct the geometry of physical processes within the central regions of these blazars.