This article investigates the use of the lexical items belonging to the complementizer phrase of relative clauses (relative CP): overt complementizer that, null complementizer o, and relative pronoun which. The research purpose was to understand whether language learners are moving toward the target norm for nativeness, in terms of the selection of lexical items in the relative CP. Two hypotheses were tested: (1) Learners prefer the [？wh] relative CP, as L2 proficiency improves; and (2) learners prefer the [？wh] relative CP more for DO RCs than for SUB RCs. Data were elicited from Korean learners, teachers, and native speakers by way of a cross-sectional production method. A picture-description instrument was employed in which the participants were presented with sets of two pictures containing the same item. The statistical results show that learners, not teachers, show a closer correspondence to native speakers, in terms of the selection of lexical items in the relative CP, and it is teachers who seem to be moving away from the target norm for nativeness. Teachers’ feature preference is more deviated from native speakers’ than learners’ in the production of English relative CPs.