Uncured Unidirectional (UD) thermoset prepregs are extensively used in advanced automated composite manufacturing processes, such as the Automated Fiber Placement (AFP) technique. Pre-consolidation is a common method for preparing uncured specimens, which is crucial for testing in-plane properties needed in numerical simulations of AFP. We aim to identify a reliable process window for vacuum pre-consolidation by examining its impact on the in-plane performance of prepregs, using uniaxial tensile and in-plane shear tests. Two key process parameters, temperature and duration, were investigated. The results show that heating during pre-consolidation significantly improves testing consistency, while excessive treatment can lead to overestimated data. Ultimately, the recommended pre-consolidation process windows are established based on the test data.