Research Findings: The primary purpose of the present study was to examine the relationship between social play and involvement in the outdoor preschool environment. The study included 173 children ranging in age from 3 to 6 years ([mean]age = 3.95, SD = 0.82) and attending 19 preschools in the Basque Country (Spain). A total of 51 teachers (50 women, 1 man) also participated. Our results indicated that there is a relationship between social participation and involvement and that group play is the type of play that best predicts greater involvement. No significant differences in levels of involvement were found between boys and girls, although gender was found to have a moderating effect on the relationship between the type of group play and involvement. Practice or Policy: The results are discussed with reference to the need to implement innovations in the outdoor preschool environment that have a positive effect on child development. The outdoor environment should promote social participation as well as gender equality and inclusion, and consequently it should be designed to offer both access to a natural environment and multiple opportunities for play. (author abstract)