Similar word to oversoon:

advanced, ahead of time, anticipative, anticipatory, before appointed time, beforehand, direct, immature, immediate, matinal, on short notice, on the dot, overearly, oversoon, preceding, precipitant, precocious, preexistent, premature, previous, prompt, pronto, punctual, quick, seasonable, soon, speedy, unanticipated, unexpected, untimely