Graphophonemic (GP) knowledge of a language represents the foundation of a good learning start point. In the English as a foreign language (EFL) context, many learners lack adequate GP knowledge of English, resulting in difficulty to master the language skills even at the tertiary level. Thus, this study investigated first-year university, commonly known as Preparatory Year (PY), students' GP knowledge of English. To do this, the study made use of two instruments -- a survey of students' answer scripts and an English GP Knowledge Survey (EGPKS). The first instrument included the survey of the Diagnostic Test answer scripts of PY students' Listening and Speaking and Writing subjects. In addition, the English GP knowledge survey was developed and administered to 252 PY students at Najran University. The results were analyzed with the crosscheck method of both instruments to validate the data and results. The results of both instruments showed that approximately 50% of the participants did not have adequate GP knowledge, which included English phonological and morphological bases. The phonological bases included graph/digraph to consonant or vowel phonemes and graph/digraph to zero phonemes, and the morphological bases included syllable division structure and adding suffixes. The study gave a close picture of the PY students' GP knowledge that would be a useful teaching resource in similar EFL contexts.