Not exactly. Carbon offsets can be applied to all potential sources of greenhouse gas emissions besides simply energy use; for instance, the methane from cows is a significant contributor to greenhouse gases. Furthermore, the offsets are essentially compensating for emissions that have already been made.
The REC, in contrast, focuses solely on the environmental benefits of renewable electricity, which produces very few greenhouse gases in comparison to alternatives. This makes RECs rather different in process and effect compared to carbon offsets.