In multicellular organisms, ranging from cellular amoebae to the human body, it is essential for cells to communicate with each other. One common mechanism to initiate communication between cells that are not in close contact is for cells to secrete diffusible signaling molecules into the extracellular space between the spatially segregated units to initiate some collective response. We formulate and analyze a class of coupled cell-bulk ODE-PDE models in a two-dimensional domain. For this coupled system, the method of matched asymptotic expansions is used to construct steady-state solutions and to formulate a spectral problem that characterizes the linear stability properties of the steady-state solutions, with the aim of predicting whether temporal oscillations can be triggered by the cell-bulk coupling. Different ranges of diffusion coefficient are considered and conditions for which the release of this signaling molecule leads to the triggering of some collective synchronous oscillatory behavior among the localized cells are characterized.