Vanillin-(6'-O-galloyl)-β-glucopyranoside (VGG), 3,4,5-trimethoxyphenyl-(6'-O-galloyl)-β-glucopyranoside (TMPGG), and (6R,9R)-3-oxo-α-ionol-9-O-(6'-O-galloyl)-β-glucopyranoside (macarangioside E) were identified as aroma precursors in oak wood. An LC-MS/MS method was developed and validated to quantify these three galloylglucoside compounds in brandies aged in oak barrels. The detection system consisted of a triple quadrupole mass analyser operating in multiple reaction monitoring (MRM) mode. For the first time, vanillin-β-d-xylopyranoside (VX) was synthesised for use as an internal standard. The detection limits (48μgL(-1) for VGG, 52μgL(-1) for TMPGG, and 19μgL(-1) for macarangioside E) were low enough to quantify these aroma precursors in spirits without any sample preparation.