In this work, we consider target parameter estimation of phase modulated continuous wave (PMCW) multiple-input multiple-output (MIMO) radar systems with few-bit quantization observations. We formulate the parameter problem as a sparse recovery problem and then jointly estimate the targets' amplitudes, time delays, Doppler shifts, and directions under the generalized sparse Bayesian learning (Gr-SBL) framework. Under this framework, this proposed algorithm decomposes the original nonlinear problem into a sequence of standard linear model (SLM) problems. Therefore, we can apply the standard sparse Bayesian learning (SBL) algorithm to solve the above SLM. Numerical results demonstrate the effectiveness of the proposed Gr-SBL algorithm for the parameter estimation of a PMCW MIMO radar systems with few-bit analog-to-digital converters (ADCs).