We investigated the effects of feedback and collaboration on undergraduates' transfer performance when using a computer networking training simulation. In Experiment 1, 65 computer science "novices" worked through an instructional protocol individually (control), individually with feedback, or collaboratively with feedback. Unexpectedly, collaboration appeared to inhibit students' transfer performance relative to individual feedback. Experiment 2 was a replication with 62 computer science "experts." This time, collaboration facilitated transfer performance. Both experiments revealed an interaction between instructional procedures producing an expertise reversal effect: Novices who worked individually with feedback actually outperformed their expert counterparts (Kalyuga, Ayres, Chandler, & Sweller, 2003). When students have low prior knowledge, presenting feedback as they work independently is more effective than collaborating with other novices. On the other hand, when students have high prior knowledge, individual feedback may actually inhibit learning and reverse the benefits of expertise. (Contains 2 tables and 2 figures.)