The Web, as a source of input, is an element that is being considered as an additional educational tool for second language learning. For an effective use of the Web for second language learning, Dodge (1988) and March (2005) suggested the use of WebQuests. WebQuests are based on the characteristics of scaffolding, socio-constructivist perspective, cooperative learning, and development of high-order skills. Previous studies have concluded that WebQuests promoted reading skills but not writing skills (Kocoglu, 2010). The present study is aimed to find out if the use of WebQuests enhances lexical richness in writing since vocabulary is an essential part of language learning skills. For that purpose, two different groups of 13 participants each were used: an experimental group which get involved in a WebQuest and a control group which performed an unguided web-searching task. Both groups took a writing pre-test and post-test. The compositions obtained were entered into the computer program VocabProfile found in www.lexutor.ca. This program is based on four word lists established in the measure Lexical Frequency Profile (Laufer and Nation, 1995). Statistical analysis showed that the experimental group used more high-frequency words at the pre-test stage, and that the control group evidenced significant progress from the pre-test to the post-test.