Place oven rack in lowest position; preheat to 350 degrees F. Process oil, garlic, lemon juice, thyme, rosemary, salt & pepper in blender or food processor until mixture forms a paste. Spread over top of roast; place in large shallow roasting pan.
Bake 1 1/2 - 2 hours or until internal temp reaches 125 degrees F., covering top of roast loosely with foil during last 30 minutes if browning too quickly. Remove beef; cover loosely with foil. Let stand 20 minutes before carving.
Meanwhile, remove fat from drippings in roasting pan; place pan over 2 burners over medium high heat. Add stock; bring to boil, stirring to scrape up any browned bits from bottom of pan. Remove from heat. Melt butter in large skillet over medium heat 2 - 4 minutes or until deep golden brown, stirring constantly & watching carefully. add stock & drippings. Bring to boil over medium high heat; boil 6 - 8 minutes or until reduced by 1/2 or to 1 1/2 - 2 C, stirring occasionally. Serve with roast.