We determined if sequence of ingestion affected USC of endophyte-infected tall fescue (TF) when cattle also grazed birdsfoot trefoil (BFT) or alfalfa (ALF). Based on chemical characteristics of TF (alkaloids), BFT (tannins), and ALF (saponins), we hypothesized that cattle first allowed to graze ALP or BFT would subsequently spend more time grazing TIP than cattle that first grazed TF followed by ALF or BFT. Sixteen bred heifers (478 ± 39 kg initial BW) were randomly assigned to 4 replicated pasture units. Each replicated unit consisted of 4 treatment sequences (TFarrow rightBFT, TFarrow rightALF, BFTarrow rightTF, or ALFarrow rightTF), with 2 cows per sequence. Pastures were in the vegetative stage of growth at a height of 20 to 30 cm and provided ad libitum forage to cattle. We recorded foraging on TF, BFT, and ALF using scan sampling of individuals at 2-min intervals. The study was conducted in 4 phases run sequentially, for a total of 30 d. In phases 1 arid 3, cattle in group 1 grazed TF pastures for 45 min and were then moved to BFT pastures for the next 45 mm (TFarrow rightBFT); cattle in group 2 grazed in the reverse sequence (BFTarrow rightTF). In phases 2 and 4, cattle in group 1 grazed TF pastures for 45 min and then subsequently grazed ALF pastures for the remaining 45 min (TFarrow rightALF); cattle in group 2 grazed in the reverse sequence (ALFarrow rightTF). Sequence of plant ingestion affected food selection. In phase 1, scans revealed grazing of TF by heifers was cyclic, and heifers tended to have more scans (P = 0.52) grazing TF when they grazed BFTarrow rightTF; scans for heifers grazing TF were consistently greater (P < 0.05) throughout phase 3 of the trial. In phase 2, heifers that grazed in the sequence ALFarrow rightTF spent considerably more scans (P = 0.03) foraging on TF from d 4 to 10 than heifers that grazed in the sequence TFarrow rightALF, and they remained greater throughout phase 4 of the trial. Although the sequence ALFarrow rightTF appeared to be more effective than BFTarrow rightTF, consistent with the hypothesis of a complementary relationship between the steroidal alkaloids in TF and saponins in ALF, tannin concentrations in BFT were minimal (1.8%), which likely reduced the presumed inactivation of alkaloids by tannins. We also speculate that heifers needed to learn about the positive postingestive influence of sequence, a notion consistent with more similar scans spent foraging BFT and TF early in phases 1 (BFTarrow rightTF) and 2 (ALFarrow rightTF), and with the consistent and marked increase in scans spent foraging on TF for animals foraging in phases 3 (BFTarrow rightTF) and 4 (ALFarrow rightTF). PUBLICATION ABSTRACT