This invention relates to blends of plasticizing oils and compatible tackifiers with olefin copolymers containing propylene, either 1-butene or 1-pentene and 3 to 14 mole percent of at least one C.sub.6 to C.sub.10 linear .alpha.-olefin which are useful as hot-melt, pressure-sensitive adhesives. The unmodified copolymer base resins have melt viscosities in the range of 10,000 cp up to about 1,000,000 cp at 190.degree. C. The addition of the plasticizing oils and compatible tackifiers to the copolymer base resin causes a dramatic and unexpected increase in the shear adhesion failure time in addition to improved coatability as well as substantial increases in probe tack and peel adhesion values of the copolymers.