Despite their potential value as collaborative knowledge editing systems, semantic wikis present a number of usability challenges for human end users. In particular, there are several mismatches between the simple user interaction mechanisms of wikis (which are the key to the success of wikis) and the need for users to create, edit and understand structured knowledge content (e.g., in the form of RDF or OWL ontologies). In this paper, we present a Controlled Natural Language (CNL) approach to collaborative ontology development using Semantic MediaWiki (SMW). In order to support the expressivity required for OWL ontology development, we extended the representational substructure of the SMW system with an OWL meta model using a template-based mechanism. To improve usability, we provided a form-based guided input interface and implemented several CNL verbalizers (CNL text generation components). In particular, we developed verbalizers for the English and Chinese variants of the Rabbit CNL, as well as the Attempto Controlled English (ACE) CNL. The combination of semantic wiki systems and CNL editing interfaces may provide an effective mechanism for promoting the large-scale collaborative creation of semantically-enriched online content.