In 1973 he quit tournament golf and has worked as a club professional in southeastern United States for the remainder of his career.
[16] The following year, in late March 1959, he entered the qualifying process for the Northern California junior championship.
[19] In April, he earned medalist honors in a match against Jefferson High School and led Capuchino to victory.
[10] In July 1959, a few months after graduation, Oppermann played the two-round Junior Chamber of Commerce State Golf (Jaycee) Tournament in Arcadia, California.
[35] Over the weekend of March 26–27 he played the two-round Blossom Festival Open in Los Gatos, California.
[57] In the semifinals he played Dante C. Vinici, a glass company worker from Ottawa, Illinois, the tournament's "upset king.
For the remainder of the back nine both players played erratically, with a number of birdies and bogeys, and Oppermann's lead remained 2 up.
[61] The afternoon's front nine was a "give and take struggle" between the two men with a number of birdies and bogeys between both players.
On the 17th hole Oppermann hit his approach into the wrong fairway but managed another "hard won par" to remain one down.
[68] His margin of victory was "the largest ever posted in the long history of northern California medal play.
"[74] He shot a final round 70 (−2) to finish in a tie for fourth place but was, in the words of a journalist, "unhappy" with the result.
[76] In early 1964, Oppermann had difficulties with his swing, "pushing the ball with his arms and turning his shoulders on the downswing.
[3] A few days later he attempted to qualify for the Lucky International Open, the annual PGA Tour stop in San Francisco.
With a second round 67 (−5) he was able to "assume his rightful pew" atop the leaderboard and take a one-stroke lead over Ron Cerrudo.
[8] In April Oppermann opened well at the Oakland City Golf championship shooting a 69 (−3), positioning himself in a tie for third, two back of Ron Cerrudo's lead.
[85] In June he entered a local qualifier for the 1964 U.S. Open at Del Rio Country Club in Modesto, California.
In their preparation for the tournament, the San Francisco Examiner stated that the "spotlight" was on Oppermann, who was expected to get one of the four berths allocated.
After 16 holes Bill had a 2 up lead but "got careless" on the 17th, hitting his tee shot out of bounds, and then bogeyed the 18th to fall into a tie.
Bill played the hole poorly, with a pulled drive and approach that hit a cypress tree and barely advanced.
Meanwhile, Oppermann made the green in regulation and hit his 30-foot birdie putt with tap-in range for a "routine par."
He opened well with rounds of 74-74-73 to put him at 221 (+5), in a tie for thirteenth, five back of the lead shared by Tommy Jacobs and Jack Nicklaus.
He shot an opening round 71 at the Crosby Clambake to place in the top ten, three back of the lead held by Joe Carr.
[135] On the 16th hole Oppermann had a chance to regain the solo lead again but was unable to take advantage of a good drive.
Though he did not win Oppermann defeated a number of star golfers, including Raymond Floyd and Gary Player by one stroke and Kel Nagle by two stokes.
In early August he began played at the Indian Ridge Hospital Open Invitational in Andover, Massachusetts.
[39] For the remainder of the year he played in six more events, making the cut in five but with no high finishes, failing to record any top-25s.
Mike Hill, Jack Nicklaus, Bob Rosburg, and Tom Weiskopf were the only players to score better.
In the opening round, he shot a two-under-par 69 to put him in a tie for third with Hale Irwin and Tom Weiskopf, one back of the lead held by Jim Jamieson and R. H.
On the back nine, Oppermann continued his "consistent play" but bogeyed the 15th and 16th holes to give "a small ray of hope to Beetham."
In the first round he shot a 67 (−5), birdieing five holes on his back nine, to take a one-stroke lead over Scott Gump and Steve LaMontagne.