Fructans are an important nonfiber carbohydrate in cool season grasses. Their fermentation by rumen microbes is not well described, though such information is needed to understand their nutritional value to ruminants. Fermentation kinetics and product formation from orchardgrass fructan (phlein; PHL), chicory inulin (INU), and glucose (GLC) were compared when fermented in vitro with mixed rumen microbes. Studies were carried out as randomized complete block designs. All rates given are fractional exponential. Significance was declared at P < 0.05, and tendency at 0.05 ≤ P < 0.10. Rate of substrate disappearance tended to be greater for GLC than for PHL and INU which tended to differ from each other (0.74, 0.62, and 0.33 h⁻¹, respectively). Disappearance of GLC had almost no lag time (0.04 h) whereas the fructans had lags of 1.4 h. The maximum microbial N accumulation (a proxy for cell growth), tended to be 20% greater with PHL and INU than with GLC. The N accumulation rate with GLC (1.31 h⁻¹) was greater than with PHL (0.75 h⁻¹) and INU (0.26 h⁻¹) which also differed. More microbial glycogen (+57%) was accumulated with GLC than with PHL, though accumulation rates did not differ (1.95 and 1.44 h⁻¹, respectively); little glycogen accumulated with INU. Rates of organic acid formation were 0.80, 0.28, and 0.80 h⁻¹ for GLC, INU, and PHL, respectively, with PHL tending to be greater than INU. Lactic acid production was more than 7-fold greater for GLC than for the fructans. The ratio of microbial cell carbon to organic acid carbon tended to be greater with PHL (0.90) and INU (0.86) than with GLC (0.69) indicating a greater yield of cell per amount of substrate fermented with fructans. Reduced microbial yield with GLC may relate to the greater glycogen production which requires ATP, and lactate production which yields less ATP; together, these processes could have reduced ATP available for cell growth. Acetate molar proportion was less with GLC than with fructans, and less for PHL than for INU. Rumen microbes ferment PHL differently than other plant sugars or fructans.