  We report follow-up spectroscopic observations of the 1.62 day, K-type,
detached, active, near-circular, double-lined eclipsing binary EPIC 219511354
in the open cluster Ruprecht 147, identified previously on the basis of
photometric observations from the Kepler/K2 mission. This is the fourth
eclipsing system analyzed in this cluster. A combined analysis of the light
curve and radial velocities yields accurate masses of M(Aa) = 0.912 +/- 0.013
MSun and M(Ab) = 0.822 +/- 0.010 MSun for the primary (star Aa) and secondary
(Ab), along with radii of R(Aa) = 0.920 +/- 0.016 RSun and R(Ab) = 0.851 +/-
0.016 RSun, and effective temperatures of 5035 +/- 150 and 4690 +/- 130 K,
respectively. Comparison with current models of stellar evolution for the known
age and metallicity of the cluster reveals that both radii are larger (by
10--14%) and both temperatures cooler (by $\sim$6%) than theoretically
predicted, as is often seen in M dwarfs. This is likely caused by the
significant stellar activity in the system, manifested here by 6% peak-to-peak
out-of-eclipse variability, a filled-in H$\alpha$ line, and its detection as an
X-ray source. We also find EPIC 219511354 to be a hierarchical triple system,
with a low-mass tertiary in an eccentric 220 day orbit.
