This document proposes a Quorum-based Medium Access Control (QMAC) protocol to improve energy efficiency in wireless sensor networks. QMAC enables sensor nodes to sleep longer under light traffic loads by only waking up during assigned "quorum time frames". Each node selects one row and column from a grid as its quorum set. This ensures any two nodes' quorums will intersect at some time, allowing communication while keeping individual duty cycles low. Results show QMAC conserves more energy and maintains low latency compared to existing protocols that require nodes to wake up at every time frame regardless of traffic.