Introduction: High-roughage diets limit nutrient intake and ruminant performance; however, extrusion alters fiber stability and degradation. Objective: This study aimed to evaluate the performance of lambs fed totally extruded diets with different roughage–concentrate (R:C) ratios. Materials and Methods: The experiment was conducted at the Small Ruminants Sector of the Universidade Federal de Uberlândia (UFU), Minas Gerais, Brazil. The experiment was conducted using twenty crossbred lambs (½ Dorper x ½ Santa Inês), with a body weight of 25.0 ± 2.28 kg and an age of 120 ± 8 days, allocated to collective pens (five animals per pen, each pen given one treatment), distributed in a randomized design and fed ad libitum totally extruded diets with different R:C ratios (60:40, 50:50, 40:60, and 30:70) at 08:00 am and 4:00 pm over 105 experimental days (15 days for adaptation and 90 days for collection). The body condition score (BCS) was determined through palpation of the 12th and 13th lumbar vertebrae to assess fat deposition, while body weight (BW) was used to calculate the average daily weight gain of the animals. Both assessments were recorded at 15-day intervals. Data were subjected to normality and homoscedasticity tests, followed by an analysis of variance and regression analysis (P≤0.05). Results: The R:C ratio had no significant effect on BW (33.67 kg; P=0.81), BCS (3.15; P=0.85), or average daily gain (ADG) over the entire evaluation period (0-90 days; 169.77 g day⁻¹; P=0.88) However, significant differences in ADG were observed between treatments during specific periods: from 30 to 45 days (P=0.01; 153.33, 125.00, 241.66, and 325.33 g day⁻¹ for R:C ratios of 30:70, 40:60, 50:50, and 60:40, respectively) and from 75 to 90 days (191.33, 168.33, 75.02, and 102.00 g day⁻¹ for R:C ratios). Conclusion: The inclusion of up to 60% extruded roughage in fully extruded diets does not compromise the overall performance of lambs.