In a madcap finish to the first day of the 106th British Open golf championship. California John Schroeder, 31-year-old son of 1949 Wimbledon tennis champion Ted Schroeder, birdied the last two holes for a four-under-par 66 and an unlikely lead in a tournament for which he had to qualify.

At 9:15 p.m., after most of the opening-day crowd of 17,600 had left the Ailsa course of the Turnberry Hotel, Schroeder rolled a six-foot putt around the lip and in the hole to move one stroke ahead of similarly unheralded Martin Foster.

Foster, 25, a rugged Yorkshireman who has earned only about $2,300 on the British tour this year, eagled the 500-yard 17th, which is named "lang whang," but was friendly today, to finish 34-33 - 67.

Foster held the lead for about four hours over more illustrious company - former champions Jack Nicklaus (1966-70), Lee Trevino (1971-72) and Tom Watson (1975). They all shot 63s on a gorgeous day when only treacherous pin placements kept the all time Open record of 65 from being assaulted.

Defending champion Johnny Miller, who said. "Those were the 18 hardest pin placements. I've ever seen in a round, but without them somebody might have shot in the 50s," was a stroke further back at 69.

Tied with Miller at one under par were Severiano Ballesteros, 20, the dashing Spaniard who tied with Nicklaus for second place a year ago, and Gaylord Burrows, 33, an Indian-born son of British parents who went to Eastern Illinois University on a golf scholarship and now plays out of Monroe, La.

Foster, 6-foot 4 and 190 pounds, is a former British junior champion who aspires to a place on his country's 12-man Ryder Cup team for the first time. Burrows, 6-2 1/2 and 170 pounds, was a cricketer of some renown in Lancashire before taking up golf at age 20 in Kenya, where his civil servant fathre was transferred.

They are interesting characters, at least briefly elevated from bit players to shooting stars in the oldest and most international of golf tournaments, but Schroeder upstaged them.

Like Burrows, he got into his first British Open by qualifying at Barassie last weekend. He shot 67-74, slightly better than Burrows, who had to win a sudden-death playoff to enter the starting field of 156.

Schroeder finished only 19th on the U.S. tour with $16,205 in winnings last year but is doing much better in 1977 with a radically remodeled game. He was reminded that his dad won the men's singles at Wimbledon in his only appearance there.

"I'd kind of like to duplicate that here," the 5-foot-10, 165-pound University of Michigan graduation, who has earned $273,897 since turning pro in 1969, said with a grin. That would be a unique footnote to Wimbledon's recently completed centenary celebrations the older Schroeder missed.

Schroeder's previous best finish on the U.S. tour was 42 ($67,257) inn 1973, but after revamping his swing he is having by far his most satisfying season. He was second to Watson at San Diego and to Ben Crenshaw at Ford Worth, and is currently 36th in the U.S. money standings with $52,880.

"I think that any golfer who is serious about his game should come and play the British Open at least once," he said after his grandstand finish today.

"I never came before because it's so expensive and I didn't think my game was suited to the type of golf played here . . . Everybody has to pinch-and-run, and I'm just learning to do that."

Schroeder's reverence for this event was tempered by some earnest criticism, however. He was in the third-from-the-last threesome to tee off, at 4:15 p.m. and after losing a ball at the eighth had to let a group play through.

By the time he got to the 14th tee, it was enveloped in a distracting cacophony of departing traffic, honking horns and poorly controlled foot traffic.

"The marshals had left and it was chaos," said Schroeder. "It was so unsettling I complained to some officials. I told them that just because we teed off late in the afternoon, they shouldn't forget us.

"I understand that most of the people come to see the major stars, but this is a great championship and all players should have an equal chance. They were mowing the greens right behind us: I don't think anybody else had to put up with that. It was impossible to concentrate."

Agitated. Schroeder pulled his drive on the par-four, 440-yard 14th, named "Risk" an' Hope," 40 yards to the left. With no shot at the green he knocked an eight-iron shot back into play, then made what he called "a marvelous 50-yard pitch" to within six inches and saved par.

That was characteristic of his scrambling 35-31 round, which carned him enthusiastic cheers as the last of the day's galleries scurried to join him along the inland back nine.

It was the 452-yard, par-four 10th that Schroeder said "turned my round around." After a mighty drive, he hit an eight-iron shot 170 yards and over the green into thick, five-inch rough. From a precarious lie he chipped in From 35 feet for a birdie - as perfect as shot as I could ever hit, as if it had eyes."

On the next hole, a 177-yarder named "Maidens," he put a six-iron shot within four feet and canned the putt. He was psyched and charging now, and not even his unpleasant experience at 14 could slow him down.

On the 17th - which Foster, Trevino and Miller all eagled while Watson, Nicklaus, and Ballesteros birdied - Schroeder ripped another massive drive, put a three-iron shot in a banker but blasted out to 1 1/2 feet and got his birdie.

He played a one-iron off the tee for safety on the 431-yard, par-four 13th, put a six-iron approach eight fee from the cup, and made "a very fortumate putt" to a thunderous ovation.

As for those more likely to remain, at the top of the leader board come Saturday's final round. Nicklaus and Watson the two betting favorites at to 1 and 3 to 1 played the best all around golf."