Autistic adults are inadequately supported in the workplace. This study sought a definition of 'reasonable' and explored facilitators and barriers to employers making reasonable adjustments. 98 employers and employees across a UK city completed a survey; 15% identified as being autistic. Qualitative data were analysed using framework analysis. Reasonable adjustments were defined as having a positive impact on autistic employees' wellbeing and work outputs without being detrimental to non-autistic employees or the organisation; they were low cost and easily implemented. Recommendations were for autism awareness training, low-stimulus work spaces, clear instructions and flexible working hours. A definition of reasonable is added to the literature, with suggestions of where to invest support efforts. Recommendations mostly apply to the education sector.