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Western juniper (Juniperus occidentalis) populations in eastern Oregon have expanded ten-fold in the last 130 years.  Such expansion is troublesome for a variety of reasons: reduction of productivity and diversity of understory vegetation, negative impact on hydrologic processes, and decline of ungulate populations through reduction of available browse.  To address the encroachment problem at the Phillip W. Schneider Wildlife Area in Grant County, OR, large portions of land have been treated for juniper control by mechanical means since 2009.  We selected areas treated in different years (2009, 2010, and 2012) as well as untreated areas that shared similar conditions of soils and topography to assess the vegetation response through time.  Vegetation sampling was conducted in the summer of 2013 in three different post-treatment conditions: interspace, duff (areas under the former tree canopy), and slash (areas under the fallen tree).  Sampling consisted of dry biomass evaluations and separation by perennial grasses, forbs, and annual grasses.  The biomass of perennial grasses had little change through time, basically resembling that of the control (80 g/m2) in interspaces.  However, in duff areas there was an increase of 15 to 50% of perennial grass biomass in 2010 and 2012 compared to the control.  In slash areas perennial grasses decreased more than 50% through time. The biomass of forbs has increased 50% to 200% primarily in slash areas.  The biomass of annual grasses has remained with little change in interspaces, but has decreased more than 50% in duff areas.  The increase in perennial grasses as well as the decrease in annual grasses in some areas are initial positive responses to juniper control.  However, plant succession is a slow process that also responds to environmental changes and requires long periods of observation.