A new enveloped following (EF) method based on high-order Obreshkov integration formula is presented. The new method is suitable for transient analysis of highly oscillatory circuits with widely separated time-scales. In addition, the proposed algorithm is capable of producing high-order numerically stable approximation of the transient response. The use of high-order formulas leads to a significant reduction in the computational time compared to low-order EF methods because it allows taking large steps in time while keeping the same accuracy.