Background <p>Optimizing nitrogen (N) fertilizer regimes in conjunction with harvesting stage (HS) (booting and milking dough stages) may potentially boost the herbage yield and silage nutritional quality of winter forage cereals (WFCs), particularly in rainfed agroecosystems. A two-season field study was executed to optimize the doses of N (0, 75, 150, and 225&#xa0;kg ha^− 1) for WFCs (barley, oat, rye, and triticale) harvested at booting stage (BS) and milking dough stage (MDS) and to improve silage quality using additives (molasses and formic acid applied at 5&#xa0;kg ton^− 1 of biomass). The trial was conducted using a randomized complete block design in a factorial arrangement.</p> Results <p>Oats produced the maximum yield contributing traits and 42% higher fresh biomass yield under the N regime of 225&#xa0;kg ha^− 1 than the control at BS. Interestingly, at MDS, oat outperformed the rest of the WFCs under 225&#xa0;kg ha^− 1 N, which remained statistically comparable to 150&#xa0;kg ha^− 1. The minimum biomass yield was noted for rye under control conditions at both HS. The fertilizer use efficiency (FUE) was maximized across all WFCs at the lowest N dose, whereas oat consistently recorded the maximum FUE and water use efficiency (WUE) at both HS across seasons. Concerning the nutritional quality of silage, the maximum crude protein (CP) content was recorded for oat in response to the N₃ fertilization regime with additives, while triticale CP contents were equal at the same level of N and molasses, whereas rye recorded the minimum acid detergent fiber and neutral detergent fiber along with the highest relative feed value in response to the highest N dose.</p> Conclusions <p>Oat may be recommended as a superior forage crop because of the highest biomass productivity, particularly under high nitrogen input (225&#xa0;kg ha^− 1). Moreover, oat harvested at BS may be supplemented with molasses as an additive to maximize the crude protein content of silage.</p>