In telecollaboration research, scholars have broadened their focus from the purely linguistic details of online intercultural encounters to include its multimodal dimensions. Yet, no study to date has explored spatial repertoires, namely the totality of semiotic resources (e.g., speech, image, objects) embedded in a particular environment and used during teaching and teacher telecollaboration. To add to the literature on this topic, this telecollaborative project invited language teachers in Taiwan and the U.S. to first use a mixed-reality (MR) simulation technology for enacting lessons with avatar students, in order to examine the spatial repertoires that unfolded during instruction, and then to reflect on their own as well as each others' teaching. Drawing on video recordings of teacher instruction, as well as lesson plans, written reflections, and post-lesson telecollaborative interactions with each other, we identified rich spatial repertoires emerging from deeply intertwined individual repertoires, from diverse semiotic resources afforded in the MR-based simulation space, and from the sequential telecollaborative tasks. The findings highlight the agentive and performative role of semiotic resources in this virtual space (especially the avatar teaching videos) in deepening L2 teachers' intercultural understanding, which indicates the potential contributions of integrating MR simulations into telecollaboration for teacher intercultural learning.