Studies have examined the benefits of offering prospective respondents to mixed-mode surveys their preferred mode option (Olson et al., 2012). However there are cost and operational reasons why a survey might request that individuals use a specific mode – via either a sequential mixed-mode design or as a single-mode design. These reasons were in effect in the Consumer Expenditure Diary Survey’s test of a mobile-optimized web diary in which household members recorded their daily expenses. The study design entailed interviewers asking eligible household members to record expenses in a diary using a mobile-optimized web mode (if they possessed a mobile phone). If they did not possess a mobile phone, they were asked to record expenses using a desktop-optimized web mode, if they had internet access. Household members without internet access were not eligible for the test. This single-mode design (from the respondent’s perspective) resulted in a variety of within-household mode combinations. This research examined three of those combinations – mobile-only households, desktop-only households and households having a mix of modes. The research describes how these three groups differed on within-household survey participation and data quality, and presents some hypotheses for the differences that were observed. Findings from the research suggest the benefits to providing household members a choice of options for online survey response.