Teaching assistants are not always utilised effectively in mathematics classrooms. Moreover, there is limited research examining instructional models that might more meaningfully incorporate teaching assistants into the teaching and learning of mathematics. To address this gap in the literature, the current study explored three distinct teacher-tutor dyads involved in a particular intervention program, Getting Ready in Numeracy (G.R.I.N.), from a single Australian primary school. All three tutors currently operated as teaching assistants in the classrooms of their G.R.I.N. teacher counterparts. The professional working relationships between G.R.I.N. teachers and their respective tutors were investigated through interviews. We outline common themes between the different dyads' approaches to G.R.I.N., and argue that all three dyads' practices are consistent with principles outlined in the literature around the effective utilisation of teaching assistants. We conclude by synthesising our findings, and presenting an embedded tutor model for the G.R.I.N. program. This model is presented as a prototype of good practice in a context where G.R.I.N. has been implemented successfully, whilst also serving as a more general model for how teaching assistants can be meaningfully incorporated into mathematics intervention programs.