A three-year study, using 84 fall-born and 28 spring-born calves of similar genotypes each year, was conducted to integrate pasturing systems with drylot feeding systems. Fall and spring-born calves were started on test in May and October, respectively. Seven treatments were imposed: (1) fall-born calves directly into feedlot; (2 and 3) fall-born calves put on pasture with or without an ionophore and moved to the feedlot at the end of July; (4 and 5) fall-born calves put on pasture with or without an ionophore and moved to the feedlot at the end of October; (6 and 7) spring-born calves put on pasture with or without an ionophore and moved to the feedlot at the end of October. A 12.1 ha bromegrass pasture divided into 16 paddocks was available. Each treatment group had access to one paddock at a time and was rotated approximately at 3 day intervals. The time on pasture was determined by forage sward heights and dormancy of the forage. In the feedlot, steers were provided an 82% concentrate diet containing whole-shelled corn, ground alfalfa hay, a protein, vitamin and mineral supplement containing ionophore and molasses. When pens of cattle reached approximately 522 kg average live weight, they were processed and carcass traits were evaluated. Cattle on pasture receiving ionophore tended to gain faster (P > 0.11), but lost this advantage in drylot (P > .10). Overall, cattle started directly in the feedlot gained faster (P < .001). Cattle receiving an ionophore on pasture had lower KPH than those that did not receive an ionophore (P < .01) and tended to have more backfat (P = .09). Treatment influenced yield grade (P < 0.001), however all treatments were YG 2. All treatment groups graded 75% Choice or higher. Cattle started directly in the feedlot were the least profitable (-46 vs 2; P < 0.001). Cattle receiving ionophore on pasture (JI, OI and SI versus JNI, ONI and SNI) were a little more profitable (5.87 vs 4.25; P > 0.9). These results indicate that cattle fed on pasture for varying periods of time produced acceptable carcasses and that carcass price was an important variable affecting profitability. Thus, the timing of marketing is critical for optimizing profit.