This dataset describes the phenotypic assessments collected in a common garden located at INRAE Pierroton research station in the South West of France (44°44’N, 00°46’W). The study compares three age structured cohorts of sessile oak (Quercus petraea) sampled in three different forests. Each cohort comprised a set of open pollinated progenies. The experimental layout was a complete block design with three replicates; open-pollinated families were randomly allocated to row plots in each block, regardless of the cohort or forest from which they originated. Sixteen phenotypic traits were assessed. Depending on the trait, assessments were made either at the single tree level, or at the plot level or at the family level. This dataset is composed of three files: The file Treepeace_SingleTree_level.csv provides phenotypic data surveyed at the tree level. The file Treepeace_Plot _level.csv provides phenotypic data surveyed at the plot level. The file Treepeace_Progeny _level.csv provides phenotypic data surveyed at the progeny level.