Chemical compounds obtained from two plants grown in Lebanon, namely Origanum syriacum (Syrian oregano plant) and Cymbopogon wimterianus (Java citronella plant) have been employed in different applications such as food preservation, and insecticidal activity. The objective of this research is to conduct phytochemical screening to identify secondary metabolites, assess the antioxidant properties of the extracts, explore their effectiveness in food preservation, and evaluate their insecticidal capabilities. Flatbread was prepared with additions of Syrian oregano and Java citronella powders, followed by analysis of moisture content, visual appearance, and sensory characteristics. Weevils (Sitophilus granarius L.) were exposed to Syrian oregano and Java citronella essential oils. The phytochemical screening indicated a rich presence of secondary metabolites in the extract. The hydro-distillation of plant leaves resulted in extraction yield of 4.3% Syrian oregano essential oil. The major component of the essential oil was carvacrol (79.30%). The Syrian oregano ethanolic extract contained 110.674 ± 1.842 mg GAE/g total phenols and 52571 ± 86 µg RE/g total flavonoids, and it exhibited a high antioxidant activity with a half-maximal inhibitory concentration (IC₅₀) equal to 168.28 μg/mL. Results showed that the powders of Syrian oregano and Java citronella have promising food preservative effects. These findings were supported by a significant decrease in fungal growth in several samples. The inclusion of a 2% mixture of Syrian oregano and Java citronella powder in the flatbread resulted in the sample receiving the highest overall acceptability mark from consumers, while also extending its shelf life. These two plants displayed effective insecticidal activity that was at its peak when Syrian oregano and Java citronella essential oils were combined resulting in 7% lethal dose (LD₅₀) towards grain weevils.