The CAP reform is an opportunity to improve the design of existing agri-environmental schemes. Understanding the design attributes affecting farmers’ choices when they adopt an agri-environmental contract can help to identify ways of increasing their participation. The aim of this article is to measure with a choice experiment, the preferences of wine-growers for different types of contracts limiting the use of herbicides in the Languedoc-Roussillon region (France). We test the effect of introducing a collective dimension in the contracts. A monetary “bonus” would be paid to each engaged farmer, provided that the proportion of land collectively enrolled in the scheme reaches a predefined threshold. Despite a high heterogeneity among wine-growers, respondents show a preference for the contracts including this bonus and are more willing to provide environmental efforts when their neighbors also do so. Then, the presence of this bonus in the contracts terms could enhance farmers’ participation.