Do you want to get the vertices from the polyshape object or from the plotted Polygon object?
pgon = polyshape([0 0 1 1],[1 0 0 1])
V = pgon.Vertices
h = plot(pgon)
V2 = h.Shape.Vertices
Note that V and V2 may not necessarily be the same as the vectors you passed into polyshape if those original vectors specified polygonal regions with collinear points, intersections, or improper nesting. See the "Area of Bow Tie" example on the documentation page for polyshape.
B = polyshape([0 0; 1 1; 1 0; 0 1; 0 0]);
V3 = B.Vertices