BACKGROUND Due to increasing demand for livestock products in sub‐Saharan Africa, increasing livestock productivity is a priority. The core constraint is limited availability of feed of good quality. We assessed optimal harvesting time of three improved grasses, two Urochloa lines (Basilisk a selection from wild population, Cayman – a hybrid, a product of breeding) plus Mombasa, a Megathyrsus selection. All are released in Latin America and Kenya or in the registration in other regional countries. We assessed dry matter (DM) yields and quality at 4, 6, 8 and 12 weeks of age in two sites. RESULTS DM yields (in t ha−1) were of the order Cayman (9.6–14.3) > Mombasa (8.0–11.3) > Basilisk (5.5–10.2) in one site, and Cayman (6.4–9.7) > Basilisk (4.9–7.6) > Mombasa (3.3–5.9) at site two. The harvesting regimes produced DM largely similar for weeks 4 and 6, 6 and 8, 8 and 12. Across the sites quality was of the order Cayman > Mombasa > Basilisk for neutral detergent fiber (NDF), metabolizable energy (ME) and crude protein (CP). With increasing harvesting interval, MJ ME ha−1 and kg CP ha−1 were inconsistent across both sites, but significant differences returned for MJ ME ha−1 unlike kg CP ha−1. CONCLUSIONS Harvesting at either 8 or 12 weeks is not recommendable as quality drops without an increase in DM yield that can compensate despite doubling and tripling time respectively, compared to 4 weeks. We recommend harvesting at 4 through 6 weeks for any of the three grasses based on yield against time, and demand at the intensified cut‐and‐carry smallholder systems. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.