The Zimbabwe School Examinations Council marked Ordinary-Level Biology examinations on computer screens from 2013 to 2017. Some examiners abandoned the 2015 marking exercise and were removed from marking teams for misconduct. Some senior examiners, who were supposed to have set the seeds and trained others, also abandoned the marking exercise. Their marking records indicated that they failed to mark significant numbers of pre-marked responses (called seeds) that were used to monitor the quality of marking, and were frequently stopped from marking certain responses. This motivated the present study that examined the seed approach to monitoring the quality of onscreen marking of O-Level Biology examinations in Zimbabwe in order to determine how seeds work in the marking of live examinations. Using the instrumental, qualitative case study design, data were collected by document review, face-to-face interviews with subject managers, and WhatsApp focus group discussions with examiners. The study established that seed parameters were set by subject managers at 5% at the item level. There was no policy to guide the minimum and maximum seed sample sizes; seeds were set by the senior examiners; qualification seeds were set and marked as practice scripts; seeds enhanced the mastery of the mark scheme; some seeds were identifiable to examiners; and senior markers set some wrong seeds, unnecessarily stopping the examiners. Moreover, there was no procedure to enforce discussions between stopped examiners and seniors. Challenges were encountered that reduced the opportunity of the seeds to identify deviating examiners.