The current study investigated the effects of four individual essential oils namely anise, clove, oregano, and peppermint or their blends (EOB), respectively at 1:1:1:1 (EOB1), 1:2:3:4 (EOB2), 2:3:4:1 (EOB3), 3:4:1:2 (EOB4), or 4:1:2:3 (EOB5) on nutrient digestibility and greenhouse gas emissions (GHG) using high concentrate (HC) and high forage (HF) diets incubated for 24 h at 39 °C. Diet samples (500 ± 10 mg) and additives were placed into 100 mL serum bottles and rumen fluid obtained from two cannulated beef cattle. Inclusion of individual or EOB reduced (P < 0.001) total gas production, GHG, and in vitro dry matter degradability. The inclusion of oregano reduced total gas production by 95.8% and 96.7% in HC and HF diets, respectively, while EOB3 suppressed total gas production by 90.4% and 92.3% in HC and HF. When compared to the control, the oregano treatment suppressed methane (CH4 ) by 99.8% and 99.9% in HC and HF, respectively while EOB3 suppressed CH4 by 99.6% and 99.8% in HC and HF. In comparison to the control, anise reduced dry matter digestibility by 11.4% and 8.7% in HC and HF, respectively. The EOB3 treatment reduced (P < 0.001) fiber degradability in the HC diet, while clove and oregano reduced f iber degradability in the HF diet. Individual essential oils or EOB decreased (P < 0.001) the production of volatile fatty acids from both diets. It is concluded that individual essential oils or their blends may be used as feed additives to reduce GHG production from ruminants. However, the use of essential oils may be combined with other feed additives to improve nutrient degradability and ruminal fermentation.