We have performed a search for gluinos (g̃) and scalar quarks (q̃) in a data sample of 84pb−1 of pp¯ collisions at s√=1.8TeV, recorded by the Collider Detector at Fermilab. We investigate the final state of large missing transverse energy and three or more jets, a characteristic signature in R-parity-conserving supersymmetric models. The analysis has been performed “blind,” in that the inspection of the signal region is made only after the predictions from standard model backgrounds have been calculated. Comparing the data with predictions of constrained supersymmetric models, we exclude gluino masses below 195GeV/c2 ( 95% C.L.), independent of the squark mass. For the case mq̃≈mg̃, gluino masses below 300GeV/c2 are excluded.