In this paper we develop a comprehensive composite meta-model from Task Analysis models called the Reference Task Meta-model (ReTaMeta model) for the purpose of comparing numerous Agent-Oriented meta-models. The reference model needed to be derived from a field independent of the Agent-oriented paradigm, yet based on Psychology. To arrive at the ReTaMeta model we first extracted the meta-models from several well-known cognitive task models including GOMS, GOMSL, TKS, GTA and also the CTT and Diane+H Task Modeling notations for fine grain task detail, and then combined their respective concepts in a complementary and comprehensive way.