A wealth of empirical research has focused on the executive function (EF) ability of autistic people. This research initially focused predominantly on establishing whether EF difficulties could be causal to the development of autistic traits. More recently, the focus has been on establishing the role of EF in explaining the life chances of autistic people. In this thesis, I aimed to test whether the conclusions drawn from traditional laboratory-based EF assessments have a bearing on the everyday lives of autistic young people. To address this aim, in Chapter 2, I examined whether the group differences between autistic and non-autistic participants on EF assessments commonly reported in the literature result from differences in the latent executive constructs underlying task performance or from task-specific, non-executive characteristics. In Chapter 3, I assessed whether group differences in EF ability emerged on a representatively-designed measure of EF. In Chapter 4, I investigated whether other metrics of real-world functional adjustment were related to individual differences in performance on both the systematically-designed and on the representatively-designed EF tasks, described in Chapters 3 and 4, respectively. In Chapter 5, I sought to understand the personal and parental perspectives about the executive abilities of autistic young people and the realities of these (dis)abilities on everyday life. Finally, in Chapter 6, I discuss how the findings from this thesis relate to the extant literature before making five recommendations on approaches I believe will move the discipline of EF research with autistic people forward. Namely, that to understand how EF difficulties relate to the lives of autistic people, future research should; (i) validate systematically-designed tasks against real-world measures with autistic populations, (ii) employ representatively-designed tasks to capture functional abilities, (iii) triangulate objective assessment with subjective reports, (iv) conduct carefully controlled experiments to elucidate the mechanisms underlying everyday executive difficulties and (v) conceptualise of EF in autism within a dimensional, rather than a categorical, framework.