Two experiments were conducted to examine the use of peppermint leaves and cinnamon oil on methane production and apparent ruminal digestibility. In experiment 1, 12 jars were utilized in a completely randomized design to conduct three separate 24 hour batch culture experiments. The objective of the batch culture experiments was to examine the effects of the selected natural supplements on methane production. For the first batch culture, jars were randomly assigned to one of the following treatments: 1) control diet (CON); 2) CON plus the addition of peppermint leaves at 3% of the diet (PEP3); 3) CON plus the addition of peppermint leaves at 6% of the diet (PEP6); or 4) CON plus the addition of peppermint leaves at 12% of the diet (PEP12). The addition of the peppermint leaves increased (P = 0.004) oxygen and tended to increase (P = 0.10) nitrogen gas, but had no significant (P ≥ 0.15) effect on methane production. For the second batch culture, jars were randomly assigned to one of the folloiwng treatments: 1) control diet (CON); 2) CON plus the addition of cinnamon oil at 125 mg/L (CIN 125); 3) CON plus the addition of cinnamon oil at 250 mg/L (CIN250); or 4) CON plus the addition of cinnamon oil at 500 mg/L (CIN500). Cinnamon oil decreased (P = 0.002) methane production when added at 500 mg/L which also decreased (P = 0.001) total gas production compared to the other treatments. For the final batch culture, jars were randomly assigned to one of the following treatments: 1) control diet (CON); 2) CON plus the addition of peppermint leaves at 3% of the diet and cinnamon oil at 125 mg/L (3:125); 3) CON plus the addition of peppermint leaves at 3% of the diet and cinnamon oil at 250 mg/L (3:250); or 4) CON plus the addition of peppermint leaves at 6% of the diet and cinnamon oil at 125 mg/L (6:125). The addition of the peppermint leaves at 6% of the diet and cinnamon oil at 125 mg/L significantly decreased nitrogen (P = 0.05) and methane (P = 0.0001) gas production compared to CON and 3:250 treatment. Based on the results of the three batch cultures, experiment 2 utilized four dual-flow continuous fermenters in a Latin Square design to examine the effects of the selected natural supplements on apparent ruminal digestibility and ruminal characteristics. Fermenters were randomly assigned to one of the following treatments: 1) control diet (CON); 2) CON plus the addition of peppermint leaves at 3% of the diet (PEP3); 3) CON plus the addition of cinnamon oil at 500 mg/L (CIN500); or 4) CON plus the addition of peppermint leaves at 6% of the diet and cinnamon oil at 125 mg/L (COMBO). Treatments for experiment 2 had no effect (P ≥ 0.17) on apparent ruminal digestibility of nutrients. There was no significant difference (P ≥ 0.09) in total or individual VFA concentrations, suggesting that the use of peppermint leaves, cinnamon oil, or a combination of the two has no adverse effects on apparent ruminal digestibility. Feeding ruminants a natural supplement such as cinnamon oil, peppermint leaves, or a combination could potentially reduce GHG production when feeding a low-quality, forage based diet.