Fifty-four Alpine doelings (initial BW and age of 31.7 ± 0.38 kg and 306 ± 1.9 d, respectively) were allocated to nine treatments individually fed for ad libitum intake of 25% concentrate and 75% forage diets (DM basis). Alfalfa was the forage in the control diet. Other diets contained Sericea lespedeza as the forage, with 1.25% DM of quebracho extract included in the concentrate fraction for a dietary condensed tannin level of 8.4%. Lespedeza treatments were no additive (L) and inclusion of monensin (I) at 22 mg/kg DM (L-I), soybean oil at 3% (L-S), coconut oil at 3% (L-N), I and 3% soybean oil (L-I-S), I and 3% coconut oil (L-I-N), 1.5% soybean oil and 1.5% coconut oil (L-S-N), and I, 1.5% soybean oil, and 1.5% coconut oil (L-I-S-N). The experiment was 12 wk with two 6-wk periods. Gas exchange was determined in weeks 6 and 12, and other measures occurred in weeks 5 and 11. The control diet offered averaged 2.67% nitrogen, 43.8% neutral detergent fiber, and 8.8% acid detergent lignin, and the L diet offered averaged 2.03% nitrogen, 42.8% neutral detergent fiber, and 13.2% acid detergent lignin. There were no treatment × period interactions for digestibilities (P ≥ 0.770) or methane emission (P ≥ 0.324). There were differences (P < 0.001) between the control treatment and diets with lespedeza in intake of DM (1.46, 1.23, 1.30, 1.18, 1.32, 1.10, 1.02, 1.20, and 1.01 kg/d; SEM = 0.059), digestibility of OM (57.4%, 50.9%, 51.8%, 52.7%, 50.3%, 52.1%, 52.1%, 51.9%, and 49.8%; SEM = 1.42), and digestibility of nitrogen (59.1%, 31.2%, 32.5%, 37.1%, 31.6%, 38.3%, 30.4%, 38.4%, and 34.1% for control, L, L-I, L-S, L-N, L-I-S, L-I-N, L-S-N, and L-I-S-N, respectively; SEM = 2.21). Ruminal methane emission was less (P < 0.001) for diets with lespedeza than for the control in MJ/d (1.36, 0.76, 0.84, 0.71, 0.71, 0.66, 0.65, 0.68, and 0.68; SEM = 0.048) and relative to intake of gross energy (5.92%, 3.27%, 3.49%, 3.19%, 2.84%, 2.91%, 3.20%, 3.20%, and 3.27%; SEM = 0.165) and digestible energy (11.19%, 6.98%, 7.40%, 6.38%, 5.90%, 5.69%, 6.37%, 6.38%, and 6.70% for control, L, L-I, L-S, L-N, L-I-S, L-I-N, L-S-N, and L-I-S-N, respectively; SEM = 0.400). In conclusion, the magnitude of effect of condensed tannins from lespedeza and quebracho extract on ruminal methane emission by Alpine doelings did not diminish over time and was not markedly influenced by dietary inclusion of monensin, soybean oil, or coconut oil.