We show that 4-year-olds assign the correct interpretation to antecedent-contained deletion (ACD) sentences because they have the correct representation of these structures. This representation involves Quantifier Raising (QR) of a Quantificational Noun Phrase (QNP) that must move out of the site of the verb phrase in which it is contained to resolve a case of verb phrase ellipsis. Furthermore, not only do children provide clear justifications for such sentences with ACD, but they treat ACD sentences differently from sentences with coordinated conjunction, a plausible alternative if they lacked QR. The findings have implications for the interpretation of experimental results in which children appear to lack this grammatical operation, and instead point to extragrammatical factors as the source of this pattern. (Contains 3 figures, 1 table and 6 footnotes.)